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Central Air Conditioner Troubleshooting & Repairs


clean air conditioner

A central AC compressor, located outdoors, should be cleaned before every cooling season.

Save energy and money while making your home more comfortable with these DIY air conditioner repair techniques.

Need help NOW? Get a Local Air Conditioning Pro Fast!

By keeping your AC unit working well, you can save energy and, as a result, money. If a central air conditioner is in ill repair, it probably won’t work when you need it most.

In addition, if your central AC works but doesn’t cool well, you’re bound to use far more energy than necessary to keep your house cool.

Several different kinds of problems can occur with a central air-conditioning system.

For example, a central AC unit can:

• Not work at all
• Run but do a poor job of cooling
• Allow dramatic changes in room temperature
• Drip or leak water
• Make strange noises

Although some central air conditioner repairs must be handled by a qualified air-conditioning repair person, in this article we’ll look at how you can handle simple repairs and maintenance yourself.

In addition, these two articles may be very helpful for the general care and maintenance of your air conditioner: Preparing Your Air Conditioner for Summer and How to Replace Furnace & AC Filters. The latter is a job that should be handled at least twice a year, before the heating and cooling seasons.

Central Air Conditioner Doesn’t Work At All

Be sure the thermostat is set to "Cool"  if your AC won't go on.

Be sure the thermostat is set to “Cool” if your AC won’t go on.

If your central air conditioner doesn’t go on automatically when the thermostat signals the need for cooling, it’s quite likely that the thermostat isn’t working properly or the unit is receiving electrical power. Before you do anything else, be sure the thermostat is set to COOL and its temperature setting is well below the ambient temperature.
Then do the following:

1Check the main electrical panel and any secondary circuit panels for a tripped breaker or blown fuse. If you find the problem there, reset the breaker or replace the fuse. A central air conditioner should be on a dedicated 240-volt circuit.

2Make sure the furnace power switch is turned on and that the outdoor condenser’s power switch, which is mounted on the outdoor unit, hasn’t been shut off. Also be sure the 240-volt disconnect next to the compressor, which is in a metal box usually mounted on the house wall, hasn’t been shut off.

With this type of electronic thermostat, you pull off the body to access the baseplate and wires.

3Turn off the power to the air conditioner and check the thermostat. Remove the thermostat’s cover and unscrew the wire from the Y terminal. Turn the power back on. Holding the wire by its insulation only, touch the bare end to the R terminal and hold it there for about two minutes. If the compressor kicks on, the thermostat is faulty; replace it or call an air-conditioning technician. If the compressor doesn’t go on when you hold the two wires together, turn the power back off and call an AC technician.

Air Conditioner Doesn’t Cool Well

If you can hear your central air conditioner running, but it doesn’t cool well, the problem can be caused by a couple of issues:

• It needs to be cleaned so that it receives proper air flow, or

• The coolant needs to be recharged by an air conditioning professional.

Cleaning the condenser unit is something you can do yourself with a little guidance. For complete instructions, please see Air Conditioner Doesn’t Cool Well.

If your room has dramatic swings in temperature before the system kicks on, see Room Temperature Too Hot, Then Too Cold.

Air Conditioner Doesn’t Blow Air

If your air handler’s motor runs but the blower doesn’t move air, the belt that connects the two probably has broken. Replacing it is an easy fix if you have a few tools and do-it-yourself skills.
Here’s how to replace the air conditioner’s blower belt:

1Turn off all power to the unit and, if the air handler is a gas furnace, turn off the gas at the gas valve that serves the furnace.

2Remove the door on the front of the air-handler cabinet to give you access to the blower (it might be on a slide-out drawer.) Check the number stamped on the belt and get an exact replacement from a home center or heating supply outlet.

First, fit the belt onto the motor pulley.

3You can usually slip the belt on the motor’s (smaller) pulley first and then start it on the blower pulley, as shown at right. Rotate the blower pulley by hand, holding the belt in place but keeping your fingers from getting caught between the belt and the pulley.

The belt should slip right into place. If it seems to be too tight or difficult to set in place, it may be necessary to adjust the motor mount to provide more slack. Then you can re-tighten the tension once the belt is in place. Check the manufacturer’s specifications for proper tension—in most cases, the belt should deflect about an inch when you press down on it.

4Lubrication. Finally, some fan motors and fans need oiling; some have sealed bearings. If recommended by your maintenance manual, oil the bearings according to the manufacturer’s directions.

Air Conditioner Leaks Water

Air conditioners and high-efficiency combustion furnaces create significant condensation, which exits through a rubber or plastic drain tube and is delivered either to a floor drain or to a small electric “condensate pump” that pumps it outdoors or to a drain. If your air conditioner leaks water or water is pooling at the base of the appliance, condensation may be leaking from one of the tubes that carry it, something may be blocking the water’s flow, or the condensate pump may not be working—if it stops working, it will overflow.

1 Make sure the condensate pump is connected to a working electrical outlet. Then look to see if one of the tubes is leaking. If it is, replace it with tubing purchased at an HVAC supply shop or a well-stocked home improvement center.

 

2 Make sure the electric condensate pump is plugged into a working receptacle, and test the pump by pouring water into its collector. The pump, which is turned on by a ball float inside that rises with the water level, should start. If it doesn’t, it is stuck or broken. If it’s stuck, you should be able to disconnect it from the power and from the inbound tube, disassemble the top, and clean it out thoroughly. If it’s quite old or broken, you’re probably better off replacing it so you don’t have to do this again in the near future.

3 If the pump runs but doesn’t empty the pan, the ball-like check valve just before the discharge tube is probably stuck. Unscrew the check valve, loosen the ball inside, and look for an obstruction. If it appears that a condensation drain tube is clogged with algae, remove it if possible (you may have to cut it and replace it later with a coupling). Blow it out or run a wire through it to clear it—or, better still, replace the entire tube. To kill the algae, pour a dilute solution of bleach (1 part bleach to 16 parts water) into the pump’s trough and pump it out through the tube.

4 Ice may be blocking the tube. If this is the case, clean or change your AC filters. If the filters appear to be fine, the air conditioner’s refrigerant supply is probably low. Call an air-conditioning technician to have the unit recharged.

For more about filters, see How to Replace Furnace & AC Filters.

Air Conditioner Makes Noise

Though most air handlers have direct-drive motors, some older units may be belt-driven. Squealing sounds from a belt-drive air handler generally occur when the belt that connects the motor to the blower slips.

In most cases, the belt is improperly aligned or worn and needs replacement. Follow the instructions above under “Air Conditioner Doesn’t Blow Air” and refer to your owner’s manual.
If a direct-drive blower is squealing or making a grinding noise, shut off the unit and call an HVAC repair technician—the motor’s bearings are probably shot.

Many heating/cooling ducts are metal so they conduct noise quite readily from the air-handling unit to your rooms. To break the conduction of sound, you can have a heating contractor insert flexible insulation ductwork between the heating/cooling system and the metal ductwork.

If you hear a pinging or popping sound coming from metal ductwork, this may be caused by thermal expansion or by air blowing past a loose flap of metal. Track along the duct runs, listening for the sound. If you find it, make a small dent in the sheet metal to provide a more rigid surface that’s less likely to move as it heats and cools.

If the furnace makes rattling noises when it runs, be sure the cover panels are screwed on tight. If they aren’t, tighten them.

HVAC professional checks the refrigerant levels in an air conditioning system.© Ernest R. Prim / Shutterstock.com

HVAC professional checks the refrigerant levels in an air conditioning system.

Getting the Work Done

If you would rather hire an air-conditioning pro to inspect and maintain your AC equipment, this FREE service will help you find a qualified local AC professional.

Call for free estimates from local pros now:
[telnumlink] 1-866-342-3263[/telnumlink]

About Don Vandervort
Author Image
Don Vandervort developed his expertise more than 30 years ago as Building Editor for both Sunset Books and Home Magazine. He has written more than 30 home improvement books and countless magazine articles. He appeared regularly on HGTV’s “The Fix,” and served as MSN’s home expert. Don founded HomeTips in 1996.

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393 Comments

  1. help! Need assistance troubleshooting my Central AC unit. Recently my AC has stopped turning itself off when it reaches the desired temperature that is set at. I hear a click where its trying to switch off but instead it keeps going. sometimes it continues to cool and others it continues blowing but not cold air. Trying to see if this is a thermostat issue or unit issue. thank you.

    Reply
    • Having the same problem. Thermostat set to off but a/c still going. Flipped circuit breaker for a/c to off. Set thermostat to heat. Furnace works fine. Will check for model of a/c. Will inquire on line about thermostat and a/c model. Might have to replace thermostat. See if this helps you.

      Reply
    • The contacts in the outside relay will weld together sometimes. I have found this many times. Turn the power off to your furnace as well as the outside condensing unit. Dissemble the relay and pry the contacts open, You should follow up with a new replacement as once these contacts are damaged, the power to the compressor is somewhat limited and the contacts will weld together again.

      Reply
  2. Over the winter, I took out the fuse unit, in case of an accidental turn on during the winter. Now I am UNABLE to find that unit! Can those be replaced? And if they are how much are they? I’ve looked for hours! I normall kept it in our laundry room and now the box I had it in is completely gone…the picture of where it was supposed to go is attached to this message

    Reply
  3. Last night I heard a noise from my outside a/c central air condenser unit. I went out to take a closer look and the sound appeared to be coming from the fan motor (a slight grinding noise that quickly got louder) I yelled to my girlfriend to turn it off. At that point I did some research and it seemed to be the fan motor (maybe a bearing) and then this morning I turned it back on to take a look again. I was assuming it would make the sound again and I could get a closer look in the daylight. However, the unit has been working all day since I turned it on the first time and hasn’t made any bad noises. It seems to be running smooth and I’m wondering if a fan motor can maybe chew up a bearing or something of that nature and then continue to work well for a length of time before it goes or what could be the situation. I appreciate any advice. Cheers!

    Reply
    • Sounds like something was loose in there and banging around…let us know if the problem happens again.

      Reply
  4. I just tightened the belt on my AC and now it doesn’t wanna blow. Is it my motor, I was thinking maybe the motor is no good, it must not be strong enough to spin the belt? I tightened it pretty tight should I lose it? Is it too tight? I should probably buy a new motor right? Any help would be greatly appreciated, please email me if possible thank you. C.pitts3522@gmail.com

    Reply
  5. The wire to contact unit outside got chewed: ac unit does not work. Can i repair wire or reconnect?

    Reply
    • If the wire is damaged, it should be replaced with one just like it. Be absolutely sure that all power is turned off before replacing the wire. Check it with a voltage meter to make sure it isn’t live.

      Reply
  6. I have a heat pump and my air conditioning will not kick on. The circuit breaker is tripped but when I try to reset it produces a grinding sound at the box and kicks off. I’ve looked for a rest button on the unit but can’t find one. I suspect the condenser is locked up? Any ideas?

    Reply
    • If turning the circuit back on creates a grinding sound at the electrical box, don’t reset it. Call a professional.

      Reply
  7. Our thermostat is set to 73. Temperature in house is 87. Temp outside is 95. Our landlord has sent several guys out to “fix” the problem, but it is a on going issue. They have installed a new thermostat, checked the cooling fluids in the system, checked the condenser, still the same. They are now trying to tell me that this is normal because of the open floorplan in the living area. The only thing, is that when we moved in two years ago, the unit would cool the area to the point that I would have to wear long sleeves, with the thermostat set to 73. It is using excessive electricity…. my powerbill is now $60.00 past last months billing, and we are only 18 days into the billing cycle. Can someone offer some guidance?

    Reply
    • Have the landlord call an AC tech. If he will not do it then you call one and have him pay the bill. Several guys are not pros. Call a pro. There are tenant advocacy groups you can call if he gives you any trouble. Your state may also have an agency. This is a breach of your lease.

      Reply
  8. My condenser is running, outside fan working, but inside blower isn’t running. Turned off the thermostat, and the blower came on, and has been running for 20 minutes. Any ideas?

    Reply
  9. Outside fan isn’t running. It blows the fuse every time we try to turn it on. The fan isn’t stuck, moves easily when moved by hand.

    Reply
    • Probably a short in the thermostat wiring. Check each wiring for a short to ground.
      A short can happen when the Thermostat wiring is pinched against the frame when the panels are put back into place.

      Reply
  10. Water leak In garag. Last time repairman told me to open small pipe and let water out. I think he told me to put bleach in it. When I let out water overflow, air comes o. And cools for a while.

    Reply
    • Please see the article above in the section Air Conditioner Leaks Water. Sounds like you need to clean out the condensation drain.

      Reply
  11. Compressor for HVAC Roof Dual Pack has a rhythmic ramping sound. Similar to this: https://www.youtube.com/watch?v=gDgqLbq1jQw
    Anyone know what the cause could be? When the fan is turned on without AC, the noise goes away.
    Beginning to think that it’s the compressor.

    Reply
  12. Need help fast!!! I know very little, if nothing at all about HVAC but I pick up things pretty quickly so any help so I can save money here is greatly appreciated. My AC unit quit working. I noticed a buzz last night from the unit. So I went inside to start trouble shooting. Inside temp was 77 and the thermostat was set to 74. The vents were blowing air, obviously not cold, and the unit outside was definitely not running. So I shut off the thermostat, replaced the batteries and gave it another go setting it to 69. Vents started to blow air immediately but again just regular air. AC unit outside will not turn on. All it does is buzz every minute or so as if it wants to turn on but it doesn’t. I can easily reach in with a stick and effortlessly spin the fan (with the power off of course). when the buzzing starts I notice the yellow wire inside actually moves. I don’t know what that means but that’s all I can see for now. I have not taken anything apart as of yet. from the exterior of the unit everything appears to look normal and its obviously still getting power (the buzz). Any ideas?

    Reply
    • Did you figure this out? We are having an identical problem!

      Reply
    • It’s most likely the capacitor, look up videos on where it is and how to safely remove it and go to a part store and replace it. I had this issue more than once.

      Reply
      • Yes it is probably the capacitor. Absolutely make sure that you shut off all power to the unit before working on this!

        Reply
    • IF THE BUZZING IS COMING FROM THE FAN MOTOR , THE START CAPACITOR IS LIKELY BAD. THE MOTOR HAS A BUILT IN THERMAL CUT-OUT SW THAT WILL REMOVE POWER UNTIL IT COOLS DOWN. WHILE IT IS BUZZING TRY TO TAKE A STICK AND SPIN IT QUICKLY, IF IT STARTS SPINNING IT’S THE CAPACITOR, IT WILL COOL FOR ONE CYCLE UNTIL IT SHUTS BACK OFF THEN WON’T START AGAIN.

      Reply
      • Thanks for stepping in to help out with these questions!

        Reply
      • Actually, the fan motor has a RUN capacitor since it is a split phase motor. If the capacitor goes bad the motor will try to run but will overheat and shut down on thermal overload. The question is—-does the compressor run? It may be more serious than just a fan motor. Also, many times, the fan motor itself will have worn out bearings causing it to overload and thermal out. My opinion is that if the motor is 10 years old, replace the motor and the capacitor.

        Reply
  13. Hi I don’t know much about stuff . My central air air conditioning isn’t working . Well I can hear it on it blows air but no cold air and the big machine outside fan thing is not spinning . And idea what it could be.

    Reply
    • MOST LIKELY THE FAN MOTOR OR ITS START CAPACITOR IS BAD

      Reply
  14. If an installer tried to charge a new compressor with coolant before removing the factory filled nitrogen , would this create any cooling problems? Such is the case with my new 4 ton compressor. Installer can not give me a reason for poor cooling performance. outside temperature 88 degrees. Lowest inside temperature 79 degrees. Seldom shuts off. Would appreciate your thoughts!

    Reply
    • I would call another HVAC guy to find out why.

      Reply
    • When installing a new unit, it is absolutely essential that a vacuum be pulled on the system before installing refrigerant! Is you contractor licensed?

      Reply
  15. My brother has an ac central air unit. When it turns on, the compressor outside always runs even when the fan inside the house doesn’t. Why?

    Reply
  16. My problem is that ac doesn’t cool well, and water is not leaking outside. when i pour it in internal unit it goes out through hose. any ideas?!

    Reply
    • The condenser unit outside may need to be cleaned or it is low on freon. Also check the filters on your furnace. If your filters are dirty it can limit the air flow through your evaporator in the furnace limiting it’s cooling ability.

      Reply
    • Also make sure the condensate drain is working properly. See the article above in the Air Conditioner Leaks Water section for info about this.

      Reply
  17. my unit wont come on the fan wont blow nothing every time they plug the compressor up it knock the breaker off what do you think is going on need help asap

    Reply
    • If the breaker is tripping every time the compressor is turned on you probably have a shorted compressor or a bad capacitor on the compressor. If you’re referring to the condenser unit outside that has the compressor in it, a shorted fan motor in the condenser can also trip the breaker.

      Reply
  18. The unit outside is coming on but the inside will not come on just makes a buzzing sound

    Reply
    • When you turn the thermostat on, the only thing that comes on in the house is the fan relay and fan. Try switching the thermostat HEAT/COOL switch off. Then switch the fan switch from “AUTO” to on. Only the fan should come on. Now if you hear that buzzing noise you probably have a bad blower (fan) or fan relay. The odds are it’s going to be blower fan.

      Reply
      • Dave, thanks very much for helping out with these AC questions. Your answers are great!

        Reply
  19. my ac wont shut off and the thermostat is blank…It didn’t go off when I switched it to OFF. I finally got it to shut down by switching it to HEAT. I think I might need a new thermostat…any ideas?

    Reply
    • Yes it sounds like a bad thermostat. The thermostat directly controls the compressor/fan relay in the condenser unit outside. This is the yellow wire connected in the thermostat. When the house calls for cooling the thermostat internally connects the yellow wire to the red wire to turn on the condenser outside.

      Reply
  20. My outside AC unit stays on even after the desired temperature is reached, after a while it gets too cold in the house and I have to turn the AC off at the circuit breaker. The Thermostat is fine, works well with furnace and used to work with AC, so I suspect a problem with outside AC unit. Perhaps a relay or Capacitors ? The contact plate looks clean, no corrosion. The unit does work when I turn it on at the breaker, it just won’t turn off automatically.

    Reply
    • Sounds like a wiring problem. Sometimes wires get “welded” together from heat…or something gets in there that cross-connects them. Or it could be the thermostat. Buying a new thermostat could be the easiest and most affordable first step.

      Reply
    • Try removing the yellow wire from the thermostat and see if it turns off. If it does you either have a bad thermostat or its wired wrong. If it doesn’t turn off most likely a stuck run relay and the condenser unit outside.

      Reply
  21. brand new unit 3.5 ton for home put in 3 months ago. it works blowing air but not cold and after an hour freezes up outside and inside.

    Reply
    • Sounds like its leaking freon

      Reply
    • Make sure nothing is blocking the air flow either outside (around the compressor) or inside (through the air filters). A kinked refrigerant line, or a blower fan that isn’t running right can cause this, too. Open all registers and make sure nothing is restricting air flow. I recommend calling the HVAC contractor who installed it 3 months ago.

      Reply
    • The contractor may have never checked refrigerant levels when he installed it, or he may have done a poor job and you have a leak. Call him back.

      Reply
  22. i turn central on….. it clicks outside in unit… fan doesnt go on nothing? is it the fan motor or condenser?

    Reply
    • sounds like the capacitor

      Reply
    • You may have a bad contactor or you may have ants in the contactor. Also, look for any wires that may have burned off where they connect to the contactor. If both the compressor and the fan are not working, check the contactor and also the breaker and/or the disconnect outside.

      Reply
  23. my central air unit was running fine I turned it off and when i turned back on it would blow but not coo, the outside unit and fan are running HELP PLEASE

    Reply
    • Make sure nothing is blocking the air flow either outside (around the compressor) or inside (through the air filters). Double check that your filters are clean. Then make sure the condensate drain is working properly. See the article
      above in the Air Conditioner Leaks Water section for info about this.

      Reply
  24. My a/c is blowing cold air and cooling the house correctly but I noticed today it’s making a loud noise outside and the fan isn’t spinning. Any suggestions?

    Reply
    • Sounds like the capacitor may need replacement.

      Reply
    • I agree with Don that the capacitor will cause that problem, but if the unit is more than 10 years old, you may need a new outdoor fan motor as well.

      Reply
  25. My central air unit was working fine for half the day, then it did not seem to be working even though it was blowing air. inside temp was 79, outside 90. I went to look at the unit outside and the copper line from the AC unit was solid, white ice. I turned the unit of for about 8 hours and then just looked at it again. line is now copper again, no ice, so I turned the unit back on. is this normal? Can anyone tell me why it froze up? Should I turn it back off and call a service to come look at it?

    Reply
    • It was iced up and you melted the ice…good job. Now make sure nothing is blocking the air flow either outside (around the
      compressor) or inside (through the air filters). Double check that your filters are clean.

      Reply
      • Thank you Don,
        Since my unit had just been repaired 2 weeks previous to this issue, the company came out the same day I called. They checked it and discovered that it was undercharged. They filled it to the proper level and it has been fine. I was not charged a dime on the repeat visit, because they had initially overcharged it and had to take some out! That left it undercharged which lead to the freezing. That is how it was explained to me anyway. This company was so friendly, understanding and professional that I would recommend them to anyone in the Colorado Springs, CO. Area.
        Rocky Mountain Climate heating and cooling ?

        Reply
        • Jody, I’m glad to hear you solved the problem—and got it done for free. Cudos to your hvac company.

          Reply
        • You got lucky! Good job. Yes, low refrigerant will cause the unit to ice up; so will a dirty filter so make sure you change them regularly, like once a month! If you don’t, you will end up with dirt on the evaporator coil and that will cost you!

          Reply
  26. Ok ? I just changed the switch on the outside unit it came on long enough to put the cover back on then it quit can anyone tell me whats next

    Reply
  27. my ac is turned on, when thermostat is set high enough so that the unit will be off, the outside unit has a constant slight hum? When I lower the thermostat to call for cooling it starts and cools fine. I replaced the capacitor and the fan and coolig start fine. It just hums when nothing is running?

    Reply
    • Maybe it doesn’t know the words. Just kidding:) Your condenser unit has a run relay in it that may be causing your slight hum noise. The low voltage control transformer in the furnace also powers the Run relay in the condenser. Try turning off the furnace power either by a local switch by the furnace or the breaker. Then check the hum. If it is gone you may have a bad thermostat. It could be causing some AC voltage leaking thru it causing it to hum but not enough voltage to pull in the relay turning on the condenser. You can also try disconnecting the yellow wire in the thermostat which is the wire going to the condenser and see if it goes away. If not turn the breaker off or pull the disconnect to the condenser and see if it goes away. If it does you will probably need a service tech to investigate further. But my guess is its probably on the thermostat side.

      Reply
    • Maybe it doesn’t know the words. Just kidding:) Your condenser unit has a run relay in it that may be causing your slight hum noise. The low voltage control transformer in the furnace also powers the Run relay in the condenser. Try turning off the furnace power either by a local switch by the furnace or the breaker. Then check the hum. If it is gone you may have a bad thermostat. It could be causing some AC voltage leaking thru it causing it to hum but not enough voltage to pull in the relay turning on the condenser. You can also try disconnecting the yellow wire in the thermostat which is the wire going to the condenser and see if it goes away. If not turn the breaker off or pull the disconnect to the condenser and see if it goes away. If it does you will probably need a service tech to investigate further. But my guess is its probably on the thermostat side.

      Reply
  28. My ac works but when gets ready to go off seems to power down then immediately kicks back on this will happen a couple times during a cycle any suggestions?

    Reply
  29. Hi my AC unit is blowing some air but not a lot. I had a tech come out and they said that the breaker outside was turned off so they switched it back on. Would the outside breaker being off still allow air to be sent through the vents? Wouldn’t being off would cause no air to circulate or still allow some air flow?

    Reply
    • He is correct. The air flow comes from the blower fan in the furance. This blower is used for heating and cooling. Also the outside condenser unit has a separate breaker used to run the compressor and fan in it.

      Reply
  30. can anyone help me… my thermostat has no power i switched it with the downstairs one and it works. so i know it’s not that… the furnace in the attic has power. I can tell by the little led lights on the control unit. I checked all the wires and they seem all to be attached… had a 3 amp fuse blown and changed that… still no power to the thermostat. I reset the power with the breaker, still no luck

    Reply
    • Quick check is to touch the red T-stat wire to the green wire. The inside fan motor should run; if it does not, the transformer in the blower unit is bad or a rat chewed the wire!

      Reply
      • that was the exact problem… it’s fixed!

        Reply
  31. I have a dual system in a two story house. Up stairs half of the vents have air coming out but the other half, all on the same side on the house, aren’t blowing any air.

    Reply
    • It sounds like either something is blocking the flow of air through one of the main duct lines before it splits off to individual registers (a damper, perhaps?), or the duct has become disconnected.

      Reply
  32. my a/c stopped blowing any air at all…the fan is working tho….a guy i know came by & said its probably the blower motor & he showed me that the motor is barely moving but i havent heard from him since….im very strapped for money already but we’re also burning up! what do i do??

    Reply
    • So the fan in the outside compressor is working but the blower in the inside air handler (furnace cabinet) isn’t? Please clarify.

      Reply
  33. Our air conditioner will leak water sometimes only. It seems like if we put it to low is when it happens. Where do we start to look for the problem first.

    Reply
    • When the weather is humid, air conditioners can produce a lot of water from condensation. Try to find where the water is coming from…is it a condensation tray or drain?

      Reply
  34. You have some great information here. Going along with your instructions for when the AC doesn’t blow air, you mention to oil the bearings according to the instruction booklet you have. I can’t stress enough how important it is to do this correctly. I’ve seen people oil it too much or not enough and it just causes more problems.

    Reply
    • Very true. Thanks!

      Reply
  35. My ac unit is blowing cold air but isn’t cooling the house. It runs all day until about 10 at night then it will come on and off fine overnight. I live in florida but it’s never done this before, help

    Reply
    • Please see “Air Conditioner Doesn’t Cool Well” above. Be sure your filters are clean and that nothing is obstructing air flow. The refrigerant in the system may need to be recharged.

      Reply
    • I agree with Don, especially about the airflow. You may need to get the inside coils cleaned.

      Reply
  36. My AC unit turns on it blows air but it isn’t cold at all. I think it might be my compressor… How do I know for sure

    Reply
    • You’ll probably need to bring in an A/C pro to check the unit and, perhaps, recharge the refrigerant.

      Reply
  37. My carrier model38brc060331 started making noise now outside unit doesn’t come on at all

    Reply
    • Wow, this could be any of several issues but the bottom line is that something inside the unit (bearings/motor/etc.) is probably going to need to be replaced by a pro. See the links above to get a local pro.

      Reply
  38. Help please!!! 5 days ago I had a A/C guy come out because my unit would not blow cool air. he said it was very low on freon and added some. he also suggested that i might need a leak sealant our something that he said he can added that might seal any leaks. So he did all of that. my air started working again and cooled the house. last night when i returned from work, i noticed that it wasn’t blowing very much air from the vents. it was like 78 degrees in my truck, and 76 in the house. the thermostat was on 70. I left it alone went to bed and this morning. the same thing. thermostat on 70 and the house temp says 76. I got close to the vents and they are not blowing very much air out. I don’t know what to do. I turned the switch to off and turned the fan to ON. the inside unit is running, but the fan out side is not spinning. What do I do, please help?

    Reply
    • If you paid an A/C guy to fix your A/C 5 days ago, call him and tell him it hasn’t been working right since his visit. Regarding the leak sealant…I’m not sure what he is referring to…is the refrigerant tubing leaking?

      Reply
    • You are low on refrigerant—-again! Low refrigerant will cause the indoor coil to freeze and you will not feel air blowing from the vents and the house will not cool. Call him back out to check the refrigerant.

      Reply
  39. I have a double wide mobile home. Last night when I went to bed, I noticed the thermostat said low battery. This morning, I changed the battery, but there only seems to be air coming out of the vents on the left side of the house (same side the unit is on). Is this a problem that can be tied to the thermostat or is it just a coincidence?

    Reply
    • Normally the thermostat would control the entire system…if it works for part of it, it should be working for all of it.

      Reply
  40. Hi, thanks for the great troubleshooting tips! I went through the steps you suggest when my AC would not cool. Changed the filter, checked the condensate drains, no water standing, pans dry, pipes dry. Changed the batteries in the T-Stat, unit tried to come on. Indoor fan kicks on, but outdoor fan had a buzz. Pushed the condenser fan a bit and it started. Let it run a bit but still not really cooling. So I am thinking that the condenser fan capacitor is bad, but would that keep the system from cooling as long as the condenser fan is running? Does the capacitor also control the compressor motor? Or do I just need the HVAC Mechanic to check the charge, change the capacitor or two capacitors? System is about 7 years old and has always worked excellent till now. Any thoughts or suggestions would be appreciated. Thanks

    Reply
    • It sounds like you’ve done about all you can do and, yes, it might be the capacitor. At this point, you should probably call an AC pro (see the links in the article above).

      Reply
    • If you are handy and know how to use a DMM, you can check the capacitor yourself with the power off and the wires disconnected from the cap. Take a photo first so you can hook it back up. Turn your meter to Ohms and touch the leads to the terminals; the meter should show a rapid change and then stabilize. It should not show open or shorted. Reverse the leads and do it again. The meter should do the same thing. Again, not continuity or open circuits. Look at the capacitors—if the top is bulged, the cap is most likely bad as there is a disconnect inside that opens the circuit when the cap bulges upon failure. An AC tech will charge you about $180 for a new one; you can buy it from Grainger for under $25.

      Reply
      • Gary, thanks so much for all of the help and expertise that you contribute here!

        Reply
  41. Hi! Thanks and here’s my similar dilemma…

    I came from Gulf Coast oceanfront, where a new central AC worked in a dandy duet with a separate central dehumidifying system. I wanted this again at in my new little condo I’m renovating that’s across the street from the Pacific in North San Diego county. I chose a reputable vendor with sensational references. He urged I just stick with a small BTU central air unit for this little condo, forget April Aire and for sure get a UV Light Air Filter scrubber in my new system. (I have allergies.)

    Things were working great! Until water started leaking down into the underground garage from the concrete’s seam in the proximity of my new indoor AC unit. Suspicious-looking: bright green hardened droplets coming out of the seam and from which the water would drip to the garage floor.

    Refrigerant leak?

    I shut off the system. Checked the air filter. Wow! In less than 2 weeks — shaggier than a buffalo! And we were only in the painting/finishing stage of the renovation!

    I won’t get tedious…but this happened again…except the air filter was FINE. I opened the closet housing the AC. A thin film of MILDEW had grown! Condensation was on the sides of the unit with puddling water standing on the flat surfaces! My AC pro is flabbergasted. Says he’s “never had anything like this happen.” He’s been doing oceanfront/high humidity homes for years.

    If ONLY I had purchased a home warranty with AC. I did not. I was not sure I was going to install it this close to the ocean. CAVEAT EMPTOR — but be sure to buy AC on that home warranty regardless, y’all!

    Next: my insurance company perform an estimate. I was reassured there was NO penalty in doing this. But I have a $1,000 deductible and this event will likely make my premium go up $500. My vendor says the labor will be $500, but he’s going to have to tear out some old drywall and a new closet interior treatment.

    the city signed off on this installation, too. I had a permit.

    I’m bumming. I like the guy! His reference are stellar. But is this a “Perfect Storm” this time? Will I have to sue him? The faulty install could be a messed-up decision on the trap and now I’m concerned prolonged water trickling has compromised the BRAND NEW TRANE system!

    THOUGHTS!??! Thanks for you help.

    Reply
  42. My Payne unit quit working. It engages but was not starting. The fan on the exterior unit was humming but not going. I used a stick to give it a start and then it worked. The fan doesn’t seem to be moving fast fast, then again I never noticed how fast it should run. I hear what I assume is the compressor trying to ‘tick’ into engaging but it doesn’t start. All I hear is the fan motor. If the fan is failing and not running like it should, could that be what is preventing the compressor from starting? It seems surprising that the fan and compressor would both stop working at the same time. Before the problem, I never had any issues and the cooling was always pretty cool so I think my coolant level is ok. Anyone have any ideas that I could try for DIY. I am the handywoman around the house, I live alone! I no way can afford a pro and would just have to go without unless it’s an inexpensive fix! ANY SUGGESTIONS?? Please and thank you! OhioKimberly@gmail.com

    Reply
    • See my suggestions above about ants in the contactor. Always turn off the power before checking any electrical.

      Reply
    • Kimberly—-for your safety, please do not advertise that you live alone. I am a former police officer and can tell you many horror stories about that. I am happy to read that you are the handy person at your house and are willing to learn and perform those tasks! Congratulations. I live in Texas but sometimes work in Chillicothe, OH at the VA center there. Good luck with your unit.

      Reply
  43. High pressure line is sweating at the start. Getting some cool,but concerned that the high side is cold.

    Reply
    • High side does not sweat. The small line is the high side; the large line is the low side. Low side line sweats.

      Reply
  44. my ac stop working yesterday checked the vent the fan is on but no cold air checked the ac unit outside it wass not turned on ckecked the breakers all ok can u suggest possible problem

    Reply
    • Some units have a fuse box or breaker box outside. Check those first. Sometimes, ants get into the contactor and block the contacts from closing. Look for ants and signs of ants. They can be really bad about that. If none of that is it, call a pro. You may have more serious issues.

      Reply
  45. We recently bought our house. Our A/c passed inspections but our upstairs A/C is not working. The outdoor compressors are running. Everything looks to be set up correctly on the thermastat but the air inside does not get any cooler. Any tips?

    Reply
    • If air is coming out of the registers upstairs but it isn’t cold, first try the steps in the section “Air Conditioner Doesn’t Cool Well” above. Be sure nothing is blocking air flow (clean filters, clean compressor coils). You used the plural term “compressors,” so you probably have a dual system. One of them may need to be recharged with refrigerant. You’ll need to get a pro for that. See the links in the article above to find a pro.

      Reply
    • Upstairs are harder to cool. The units are generally sized by square footage and upstairs are usually smaller than downstairs so they get the smaller A/C unit. That can be tragic since in southern climates (not sure where you are) the upstairs can get brutally hot and the unit will not cool it down. First, check to make sure the upstairs unit is actually running—not just the outside unit, but the inside unit as well. Then, check the ducts to make sure they are insulated and the insulation has not fallen off (if they are metal ducts). Feel the air coming out of the registers and use a thermometer if you have one to see what the air temperature is. Make sure the filter is clean. Other than that, you may need professional help.

      Reply
      • Great advice. Thanks, Gary.

        Reply
  46. My central air unit is making a loud humming sound, the fan in it is not turning and the coils fill quite hot. there is air coming out the registers but not cold.

    Reply
    • Is it the fan in the air handler (inside) or the compressor (outside) that isn’t turning? Also, which part is humming?

      Reply
    • The outside compressor unit’s fan was stopped but there was a loud hum coming from it. I shut the system off and about 16 hours later I turned the it back on and it worked fine and has been working well ever since. Strange!?

      Reply
      • You may need a capacitor for the outdoor fan unit, but most likely you really need to replace the outdoor fan motor. It is not hard to do but be sure to turn off the power before you do it. The motor is less than a hundred bucks; you can get it at Grainger if you do not have any other source. Once installed, make sure it is turning the right way—if backwards, look at the wiring diagram on the side of the motor and it will tell you which wires to change.

        Reply
  47. our AC is working well but when we turn it off on the thermostat while fan setting is in Auto mode, there is still air (ambient temp air since AC is off) coming out the supply diffusers and air coming out the return. Is this normal that even AC is off, air is continuously moving in and out our house? Is this continuous moving air or continuous fan movement consumes a lot of electricity? thanks…

    Reply
    • It sounds like the fan switch in the thermostat needs to be turned to “Off.” See if that works.

      Reply
    • Air should never come out of the return! If air is coming out of the system, listen to your unit inside to see if the fan is running. If it is not running, you may have a hole in a duct and outside air is blowing into the system.

      Reply
  48. The ac is working great but, as I was cleaning out the registers I noticed water down inside the ducts. Never noticed this before. Is this a problem?

    Reply
    • If hot air is leaking into the air duct, condensation can form. Or, the duct may be undersized for the air flow. Either way, you should probably have an AC pro check this so that you don’t end up with problems of mildew or mold. See the links in the article above to find a pro.

      Reply
    • Make sure the ducts and the register boxes are insulated. Ducts are like a glass of iced tea sitting on the table. The outside of the glass gets wet from condensation. The ducts do the same thing and sometimes drip water if they are not properly insulated.

      Reply
  49. I have a split level house ,the lowest level is very cold ,while the bedrooms upstairs are uncomfortably warm. Any tricks ,I already closed off dampers ?

    Reply
    • Do everything possible to minimize the amount of heat getting into the house, and then try using fans (and turn on the fan switch on the thermostat) to keep the air moving from upstairs to downstairs—presuming that there is at least one “cold air return” register upstairs.

      Reply
  50. I replaced the compressor and the fan isn’t working still? Also the vents are blowing air and I turned the ac off any suggestions?

    Reply
    • Are you referring to the fan in the compressor? If so, it sounds like it isn’t getting power. The vents will blow air with the ac off when the “fan” setting is turned on in the thermostat.

      Reply
  51. My air conditioner indoor unit fan runs correctly but its not blow much strong air on on the left side. Some times air flow from fan increase and decrease continuously. What is the problem actually? Can you help me out?

    Reply
  52. I cleaned my central air unit removed cover it ran good for 15 min. was cooling good then stop ! I removed the breaks insert them back in fan start to move slowly then stop and just had a humming sound ?

    Reply
  53. My hose that goes from my air conditioner to my house is freezing up…..what does that mean?

    Reply
    • This can happen if air flow is restricted by dirty filters, blocked vents, dirty coils, etc.

      Reply
  54. Note in the “Air Conditioner Leaks Water” section above that some condensate pumps will shut off the system if the pump isn’t working (shown in left photo). The stand-alone condensate pump shown in the right photo is about $50 and you can buy it by clicking on the photo. And, yes, there is a relationship between the pump and the system…the system may not cool effectively if the condensate drain is plugged.

    Reply
  55. My central air conditioner unit is not making any condensation. I know it should make several gallons per day so it has me a little worried. Is there a specific problem that would cause this?

    Reply
  56. I have 2 central air units. They are working fine. I decided to go up to the attic where the air handling units and evaporator coils are located, to make sure the condensate drain pans looked OK. One unit, the smaller one, has water in the drain pan and the overflow goes to outside like it is supposed to. The main unit, however, which runs a lot here in Oklahoma summer weather, has an absolutely dry drain pan. Where is the condensate going?

    Reply
  57. Most likely your indoor coil (the evaporator coil) is dirty. Even with filters, some dirt and animal hair gets past the filter and eventually stops some of the airflow. Reduced airflow whether it is caused by a dirty filter, dirty coil, dirty squirrel cage blower, or bad fan motor will cause the coil to freeze up blocking the airflow completely. If all that is correct, you need to call a pro to check the refrigerant level. There are only two things that cause a unit to freeze up; they are reduced airflow over the indoor coil and low refrigerant. If the refrigerant is low, you may have a leak.

    Reply
    • Gary, thanks very much for weighing-in on this. We really appreciate your help and your expert advice!

      Reply
  58. instead of buying a new Electric Condensation unit can I just route a hose from the water supply to a drain and remove the unit altogether. If so will the AC still work

    Reply
    • Pumps are needed where the condensate drain water can’t be carried by gravity so, yes, you can just run a hose from the condensate collector to a drain as long as it only goes “downhill.”

      Reply
  59. Central A/C runs but does not cool. New filter put in just now, cleared water pipe, did all that was listed except call repair might need freon or what ever. Has been 21 years since installed.

    Reply
  60. my ac unit keeps kicking off and what I mean the outside fan stops working and it just hums and don’t spin I can go out and take the outside fuse panel and pull out and put it back in a few times and also help the fan spin and it will work again for a while could you help with my issues thanks

    Reply
  61. Thank you for answering my question about the Air cond and hose

    Reply
    • My pleasure, please return to HomeTips often!

      Reply
  62. Gary, correct me if I’m wrong, but it sounds like there might be a blockage. Curtis, try to see inside the unit to find where the ice starts to occur—maybe right after an in-line filter.

    Reply
  63. Hi Don and everyone- thanks a million for all the helpful info! It helped me eliminate what the problem is not, but I still don’t know exactly what it is. Brief description of the issue that started yesterday:
    Thermostat set at 75 seems to be working exactly like it should and switches on the compressor and fan, but the fan shuts itself off after only 26 seconds each cycle while the compressor keeps running. Then the fan kicks on again a few minutes later for another 26 seconds and quits again. The house temp is about 83, so it seems like the compressor is getting the message to keep cooling from the thermostat, but something is telling the blower motor to stop. The capacitor is good- tested with a meter- and I bypassed the t-stat and got the exact same result, so I know it’s not that either.

    So, seems like that leaves either the blower motor or the board. I’m guessing the board, because the blower switches on when it should and has not tripped any breakers or fuses – it’s just getting a signal to shut off from somewhere (prob the board). The blower does the same exact thing when the cooling switch on the thermostat is off and just the fan is switched on- 26 second run cycles every few minutes. When the thermostat is switched to cool, I can hear and feel the coolant cycling through the high pressure side before the blower kicks on. Is this a sign that there is air in the system and not enough coolant? Could that be the problem? It’s an older system from 1999.

    It’s supposed to be over 100 here the next few days, so any info or direction would be very much appreciated! Thanks!

    Reply
  64. My ac froze up a couple times this summer and I cleaned the filters which seemed to work but today I turned it on and it sounds like it’s running fine then it sounds as if it shuts downs then cycles back on again then shuts down again (I turned it off at that point)

    Reply
  65. The air coditioner works well all day except for once or twice a day it makes a lound vibration noise. I turn it off and restart it and it sound alrigt. It’s so loud that it vibrates the house wall next to it. What’s wrong?

    Reply
    • Our unit, a Lennox , was installed a year ago . When the ac turns on it sounds as if a small bomb has exploded. The unit installer says this is normal. Is it?

      Reply
  66. AC motor runs but only blows cool air if fan on thermostat control inside is turned on continuously. Any suggestions?

    Reply
    • Hmmm…check the wiring of the thermostat. You can probably get specifics by searching the make and model of the thermostat online.

      Reply
  67. When my ac is turned on it starts fine – cool air starts to flow – but then the outside fan starts to slow down and comes to a slightly squeaky stop. Then the motor just whines until turned off. Could it be the bearings?

    Reply
    • Definitely sounds like the bearings. Too much friction. When it overheats, it triggers a thermal shutoff switch. You probably need to replace the motor…and maybe the capacitor.

      Reply
  68. I have a Tempstar 2 1/2 ton a/c. The compressor fan motor went out. I live in Houston and cant go without a/c. The tech replaced the fan motor (a universal, since my unit is discontinued) and the capacitor. I was charged $695.00. I feel like I was over charged. Can you tell me if this seems like a fair price to you? Thanks for your time and look forward to your reply.

    Reply
    • Cheryl, unfortunately that is in the ballpark of averages, particularly in a busy AC season. For parts and labor, the motor typically costs from $300 to $500 and the capacitor from $150 to 300. It’s always best to get an estimate before the repair person starts…but I know you’re already invested by the time they come out to the house.

      Reply
    • Cheryl, I don’t know what Don is smoking, But I just bought a capacitor for $10 + change. You were WAY over charged on parts, but probably really overcharged on labor. A/C companies really try to take advantage of people in need & they charge what they want, or, can get away with. For the future, try networking with friends to find a contact that either works for a company or a municipality in this field, as they often work after hours because THEY are not the ones pocketing the money they (the company) got from you. FYI

      Reply
      • Hi Jerry, thanks for commenting. You’re right that you can buy a capacitor for very little. I was referring to the average costs for parts and labor—the latter being by far the most expensive, particularly in the height of the season, as you point out.

        Reply
  69. any reasons a central air fan would stop running intermittently and won”t t run until the fan is spun manually?

    Reply
    • yes, that means you need to replace the capacitor. Very easy and cheap fix. You can youtube how to change. It takes 5 mins to do.

      Reply
      • Amy, thanks for helping out. Good advice!

        Reply
  70. blower in the heat ex-changer sometimes will not start. Outside pump is running. Shut the system off and re-start and the blower starts. Relay or maybe capacitor??

    Reply
  71. I have changed out the capacitor and contact switch. The fan turn on when I push the reset switch in but then it turns off again. I thought the old contact switch was bad but it is still doing the same thing with the new contact switch.

    Reply
  72. my automatic condensate pump is not working and is hot and it smells like a burned transformer. says it has safety switch. where is it and can I reset?. My whole furnace and a/c won’t work?

    Reply
  73. Earlier today I moved some things over by the air handler and something knocked the drain pipe loose. There was water around the base of it which happens to be galvanized to the floor. Nothing is working, air condenser, air handler or thermostat. Breakers and and fuzes aren’t blown or tripped, yet nothing is working. I’ve turned all off for the suggested 2 minutes, nothing; and also manually did the Y to R contact for over 2 minutes. Older thermo with 5-7 wires connected in one way or another. No resolve as of yet, could it be possible that the puddle caused it to arc out after making ground contact because of the water puddling around and under the air handler? Please help, I’m in a sticky situation as we have another week before we move due to foreclosure process blind siding us from landlords lack of paying mortgage payment for years. He’s dropped all responsibility and the bank will step in on oct 8th. We’ve got 4 more days before moving to the new rental we have secured. Meanwhile my wife and I take care of a 50 yr old mentally handicapped and it is an issue jeopardizing our legal guardianship of her. I need educted advice for a temp fix for the next 4 days at the least. Please!! I am begging for help here. I can’t find my hot wire tester (tig tester) so this is quite difficult as it is without knowing whether or not there’s power there to single out a problem internally. Or if the power isn’t present which means that’s the entire issue in itself.

    Reply
    • Sure it was a drain pipe and not a cooling line?

      Reply
      • You would definitely know if it was a refrigerant line.

        Reply
    • There is a float switch in the air handler that will shut it down if the condensate water lever gets to high. Clean the drain system and check the float.

      Reply
  74. When we get a heavy rain, the a/c unit makes a loud noise when it runs. Almost like a thumping sound and you can hear water. The noise comes from where the filter goes. Any ideas?

    Reply
  75. Whenever my unit kicks on, it temporarily knocks my modem and a couple other devices out. Believe it is drawing too much power, but don’t know why.

    Reply
    • Is your modem plugged into the same circuit that powers the AC? If so, you need to plug it in to a different circuit or consider getting an uninterruptible power supply (UPS). AC units draw a lot of power and this surge is enough to mess up electronic gear.

      Reply
    • Please check you ground. Check everywhere beginning at your service box and then at each receptacle or junction for all the lines powering the devices in question. Quick test, put a light bulb (old school bulb not a CCF or LED) into the power socket powering the modem. Turn on A/C and note if the bulb changes intensity. It should not vary much at all. Either brightening or dimming indicates a problem. Strangely enough the brightening usually means the ground is at fault. Dimming can also mean poor connections or damaged wiring, but as you have suspected, it can also be a worn compressor drawing too many amperes. Perhaps there is a professional here who can elaborate more completely on this issue. P.S . ALuminum ground wires are quite often the culprit since they corrode at connection points or anywhere weather or moisture can come in contact. Good luck and follow all safety rules and common sense.

      Reply
  76. I’ve never been on one of these chat places before so please bare with me. I am alone here in Florida and moved into an apartment. Soon after moving in my apartment became very damp and cold the air soon after begin to smell musty and within a few days it was very uncomfortable to be sitting here in the apartment. I went to the apartment manager and he send a technician over who said there was nothing wrong. Soon after that I got down on the floor to find out my rug was very damp I went out and bought a basement size dehumidifier within hours the bucket was full and this continues to be a daily issue. I have approached management on several occasions and they throw up their hands and say all the tests are normal and they don’t know what to do if anything. I also want to add that the water coming out of the bucket from the dehumidifier has a smell to it which I can’t identify. Does anybody have an idea as to what the problem might be I am NOT going to let this drop and will keep pursuing it but I’d like some kind of an idea if anybody has had this issue what they did to resolve it.

    Reply
    • Is your apartment floor at the bottom of the building—on a concrete slab?

      Reply
    • Yes it is. I have a neighbor right next to me and she is not having the problem I have and our apartments are connected

      Reply
  77. I was replacing a filter in the inside Handler and the filter was wet. In searching most often is said the drain is plugged. My drain from the handler goes into the floor. I poor vinegar into the upper part of pipe regularly. Today I used hose and sent water down the pipe..it seemed to go ok. I went outside and by the compressor is a pipe. This is often mentioned in what I have read to be the drain, but I have the floor drain. Nothing came out this pipe when I used hose. Also read about vents. Could this be a vent to my washer??? All very confusing….

    Reply
  78. When I switch my thermostat from cool to heat, it blows the fuse in the air handler. Please help!!

    Reply
  79. I have a “gas pack” in NC. Last night we noticed the house was not cooling to the set temperature and it was starting to warm up again outside. First thing I checked was the floor vents to make sure air was blowing. It was not. Went outside and the condensing unit was running but the compressor was freezing up. I thought it might be a belt on the blower motor. So I shut the unit off for the night. Woke up this morning and turned it back on. Darn thing started working just fine. How is it that the blower was not working, the compressor was freezing up, but today it is all working as it supposed to? Makes no sense to me. I’m sure it didn’t fix itself and the problem will likely pop back up again. Suggestions?

    Reply
  80. My heater worked great last winter but this winter it won’t kick on.
    I do not have the old style pilot light and my central air unit ac side works great and blower fan works great also.
    When I turn up thermostat I hear a click,then a hum but no ignition or fire burning so I think my ignition has went out.
    How do you I check and or replace ignition?
    It’s a 1997 Coleman heater ac unit propane.
    Any suggestions?It has a window to see fire but there is no fire of sparks that I can see when thermostat is turned up.
    Thermostat works on ac and I cleaned and checked all the contacts on thermostat,so I think thermostat is fine.

    Reply
  81. Outside unit is kicking on and off at 7 second intervals.

    Reply
    • Short cycling may be caused by an improper thermostat heat anticipator setting (see Thermostat Repairs at http://www.hometips.com/repair-fix/thermostat-temperature-wrong.html, a refrigerant leak or improper charge, by icing over of the evaporator coil, a malfunctioning control board or a couple of other things. If it isn’t the thermostat, you’ll probably need a pro to resolve this.

      Reply
      • Improper filter maintenance by not keeping it cleaned can cause dirt and debris to bypass the filter and block air flow through the coil. Another possible cause for short cycling, and icing of the suction line coming our of the air handler.

        Reply
  82. National AC contract replaced my evaporator coil because they said it was falling apart and clogging the drain (unit is 3.5 years old) when they pulled the evaporator and box out of the attic it had a little rust on the coil end supports but everything all the remaining aluminum looked good. Did i just get taken? If so what recourse do I have?

    Reply
    • Sounds strange to me. The unit should last a lot longer than 3.5 years. Why was the evaporator coil falling apart?

      Reply
  83. Got a head scratcher. A couple of days ago I tried to start my AC…unit was turning on and blowing air but outside fan would not run. I cleaned coils and replaced capacitor last night but when I turned power back on and tried to start up, the AC unit in attic (that was previously working fine and blowing air) would not come on. Checked power at panel and tried resetting several times. I even went back to the old cap to ensure it had nothing to do with the new equip I installed but still no luck. I have since put the new cap back on but have no idea what to check from here. Note–on the furnace in the attic there is a switch that must be engaged for unit to start. It usually clicks when engaged whether it starts or not. The switch will now not click at all. I tried bypassing the switch with jumper wire but still no luck. Any suggestions would be greatly appreciated. At this point I’m not even sure if the first problem was solved. I could still have a bad fan motor and a bigger problem on top of it all. Thanks in advance!

    Reply
    • Trent, it sounds like the power has been interrupted somewhere…loose wire, bad switch…etc. I hope we can get an HVAC pro to weigh-in on this problem because there are so many variables.

      Reply
    • Sounds to me like in the process of replacing the capacitor, you moved or disconnected a low voltage wire that runs the air handler. You did not say whether the compressor was running, and the fan not running in the outside unit. If the run capacitor was faulty, you should have heard the fan humming.

      Reply
      • Pat, thanks very much for helping our community!

        Reply
  84. Make sure the main circuit breaker and service switch by the unit are both on. Beyond this, there are other safety switches in the unit (high and low pressure safety switches, motor overload reset, etc.) that may have switched off. If you’re not familiar with this type of equipment, please call a pro.

    Reply
    • Did you turn the service valves back on to pressurize the system?

      Reply
  85. Yesterday I noticed that my fan will stay on when my AC is off. I have shut off unit completely so I don’t burn out the motor. Any suggestions as to why this suddenly started happening? And what can I do about it. Any help will be greatly appreciated. Thank you

    Reply
    • The contacts could be welded together keeping the fan running, but not the compressor. Replacing the contactor or gently pry the contacts apart will probably fix it. A new contactor would be best.

      Make sure you turn the power off before messing with the relay/contactor

      Reply
      • Thank you very much for responding..I am wondering why this would just start happening…Do the the contacts sometimes move together by themselves? It was working perfectly before…I will try your suggestion..thank you again…Have a nice day!!!

        Reply
        • They arc when making or breaking. As the wear increases, so does the resistance, thus increased arcing as well. Return springs wear out to the point that they don’t open the contactor fast enough to prevent prolonged arcing. Just a few causes and when the welding occurs, it’s instantaneous without any warning.

          Reply
          • This is an awesome answer!

  86. So my first posted question disappeared. I have two central a/c units, one cools the upstairs and one the downstairs. The upstairs a/c unit is the smaller of the two. This is the one that has the problem. The a/c unit cools the upstairs as it should. Cycles as required on temp. The problem I have is when the temp is reached and the thermostat kicks the a/c unit off outside, there is still a him coming from the outside unit. If I switch the thermostat to the off position, the humming goes away. If I switch it back to cool, it starts humming again. Any thoughts what could be wrong and what to check?

    Reply
    • The humming could be the low voltage transformer, it the outside unit is also the air handler. Otherwise it probably does not have a transformer on the outside unit. That is the only device that has power to it when it is not cooling. Just guessing as I’m not there to meter the unit.

      Reply
      • Pat, Thanks VERY much for weighing in with your professional answers! It’s really great having an expert HVAC guy like you helping out our community!

        Reply
  87. My outside unit won’t come on. I had someone check the capacitor and it was fine. If I push the shunt in on the contact in the outside unit it will start. It just won’t hold. I checked that contactor but I didn’t get the 24 V on the low voltage side coming in. Where do I go from there as far as checks on the low voltage side. How do I check the transformer and everything else?

    Reply
    • did you check the door switch on the furnace? Could be a transformer issue, but if the inside air handler, (furnace blower) comes on, then it’s not the transformer. Then check the thermostat settings, and the stat.

      Reply
  88. My a/c was running today, and it made a popping sound, and when i took the front panel off the a/c and furnace unit and it had some water inside. what might cause that

    Reply
  89. It would seem that in conjunction with issue #1 the author should have added to check the capacitor. The capacitor in these units is a combo for use in starting both the condenser and the fan. If the capacitor is failed the A/C unit will not run. It’s very easy to test. Before opening the electrical cover on the A/C unit be sure to shut all power off and verify. Now pull the cover off and with a digital multi meter set to capacitance, put one lead on common and the other lead on one of the other two. You should read a number and not OL which shows a short. These capacitors are basically two capacitors in one with both sharing the common leg.

    Reply
    • Roger, thanks very much for this! We will add it to our article. Please come back to our community here at HomeTips often!

      Reply
  90. I had my AC running for almost 5 years and until today it is in good condition. Thank you for this wonderful article.

    Reply
    • Thanks for visiting HomeTips—and thanks to our community members like Pat McBride who come in and help answer questions with their expertise!

      Reply
  91. Today my ac turns on and you feel the air but it doesn’t get cold could it have over heated it was working fine yesterday any suggestions on what it could be plus it makes an ugly noise when I turn it on or off and I already changed the filter for it

    Reply
    • Not much information to go on, but It sounds like your fan in the condenser, (The outside unit), could be the problem. You need to tell us where the ugly noise is coming from to help you.

      Reply
  92. My air handler is new as of last year and my outside condenser is in pretty good shape. The vents inside the house are shooting out cool air with a force to move your hair, but two things: it is not circulating well throughout the house, and the temperature is constantly fluctuating between 78-85 degrees when the thermostat is set to 74. It never even gets close to that temperature. Additionally, the refrigerant line is leaking non-stop. I was pretty sure it was condensation at first, but come on, 3 bowls daily to empty out or it’ll overflow? Is there something wrong with the refrigerant line? Could that be the cause of the improper circulation and lack of cooling?

    Reply
    • Wow. You have some serious issues. First of all, is sounds like you could possibly have too much air moving across the coil. If the air moves too fast, it will not pick up the cooling on the coil. You should see a 15 to 18 degree difference between the ambient air in the house, and the discharge air from the closest discharge vent to the air handler. No more than a degree or two difference as to what I stated. It may vary more when the house is extremely hot and full of moisture..

      I don’t think you have a refrigerant line leaking, especially as much as you say there is or that unit would not run but a few hours before shutting down on safety pressure switch’s. Refrigerant in an AC system carries oil with it. You would see an oily liquid and it would smell. Also it would evaporate instantly and would freeze burn you hand if handled.
      I believe you are looking at the condensation line from the evaporator coil, and if your house is 85, your talking about a lot of moisture in the house and it takes a long time for your AC to remove that moisture. 3 bowls of water is nothing to what is in your home.
      AC’s will not really start cooling to any degree until it removes the moisture, and your talking gallons of water, not bowls. That is it’s hardest work. Dry air is much easier to cool. If you air handler is in the attic, it should have a drain pipe to the outside or a drain in the house. Again, lots of water will be removed from the air..
      The air needs balanced according to CFM needed in each room determined by the cubic feet of the room. Who ever installed that air handler needs to come back and make it right. Balancing air movement is part of the job of installing an air handler.

      Reply
  93. I enjoy using my past experience to help folks and exercise my memory. I am retired now so this keeps me in touch with my past troubleshooting skills. But…………I find that I am answering questions that are years old. I did not pay attention to the dates until recently. I feel foolish in doing that, and don’t know why these years old questions are being posted today.
    Hope someone here can help me to understand this.
    Pat

    Reply
    • Pat, all questions get posted and we haven’t had an expert like you on the site to help answer them. Your answers here have made a tremendous difference in helping people WHEN they need the assistance. But also know that many visitors have the same questions, so your answers are helping people now and in the future. Thank you!

      Reply
      • Thanks for that explanation Don. I understand your meaning and agree.. And with my love of the trade, I feel good in exercising my past skills, and to help folks out. There are a lot of people that cannot afford the high cost of techs and have the skills to make some repairs themselves. And those that just want to be able to make their own repair. I was always one of those. I don’t intend to take food from the folks that make a living in HVAC. But still there are those that cannot afford a service call.Also those that get taken advantage of by shady repairmen.
        Thanks Don.

        Reply
  94. My a/c takes for ever to cool house off and can barely feel air coming out. Checked the unit in attick can see motor/fan running, no ice or water build up brand new filter, fan on unit outside spining line going into house is cold to the touch. Any suggestions?

    Reply
    • The small line from the outside unit, (the condenser) should be warm. If the house is very warm, the line will possibly even be a bit hot. The larger line, (the evaporator line) should be cold to the point to where you feel “flashing” very cold. And this line should be sweating. If you don’t have this condition when the house is close to desired temp, then you could be low on refrigerant.
      The discharge air coming out of the closest vent to the air handler should be about 18 to 20 degrees colder than the ambient air temperature in the house. Any higher or lower than that indicates an issue either with a low charge or air blockage in the condenser or the air handler. Too low discharge temp indicates low air flow through the air handler, and higher temp may indicate a low refrigerant charge. Open up the air handler and check for a clean coil, and loose fan belts not moving enough air. Also look at the squirrel cage fan blades for dirt build up.Good luck

      Reply
  95. My A/C not cooling the house. i had a technician come onsite and have him verified. he said nothign wrong with the system and enough coolant there in, however he said there could be blockage. he suggested me to contact manufacturer. can you please suggest what is this blackage could be ? and how can i fix it. i tried to reach manufacturer but no help.

    Reply
    • It’s strange to me that a technician would come out to the house, check the system, and leave without diagnosing the problem or faulty part and without being very specific about what needs to be replaced. Does the system run but not blow cold air? Does it blow any air at all?

      Reply
      • it blows air but the as usual as it does. technician touch the freon pipe out side and said it is cold and did the same at the other end of the inside unit and said it is not cool. so he concluded that there is a major block and he cant do anything and advised me to contact the specific company who deals with this kind of model( payne)

        Reply
        • That is good advice. You need a technician that will get deeper into the problem and the dealer of that brand will be more experienced.

          Reply
  96. the motor fan in the attic doesn’t come on often. I change the capacitor and it worked for a few days then the compressor is still on and the line leading to the house is frozen. what can i do to correct this continuing problem.

    Reply
    • Sounds like a possible defective fan contactor or a damaged fan motor. You need a service tech. Again, a frozen line to the compressor will eventually do a lot of damage. Much cheaper to fix it now than to replace a compressor.

      Reply
  97. Hello, we recently moved to a new house (2 floors), we have two AC units, in the bottom floor the AC works fine, however on the top floor it is a mess, during the day the temperature stays around 80 degrees never goes below 79 (we set the AC to be 75 but it never makes a difference), the compressor and the fan are working, and there is cool air coming out from the vents, however the AC is never able to cool down the top floor below 79. at night we set it to 78 and it is fine in 2 bed rooms, however there is also another problem, in the master bedroom it is cooler there, in the other rooms it varies between ‘ok’ and boiling hot. the filters are brand new btw. usually the AC stays on all day cuz it never reaches the desired temperature. i would appreciate any help here, thank you !

    Reply
    • Mike, this is not an unusual problem. Because heat rises, all the hot downstairs air is rising to the upstairs and overworking the system, which may be undersized. In addition, your attic may be under-insulated. Is there much air flow in the rooms that don’t cool well? If not, try to check the ductwork for dampers that may be partially-closed , restricting flow. If there is plenty of air coming out of the registers but it isn’t cold, I’m going to guess that those rooms are pretty far from the air handler and that the ducts may not be insulated. Maybe they pass through the hot attic, where the cold air gets warmed. Does that make sense? Insulating the ducts may help. I think you’re probably going to need to get an HVAC person in there to check out the system.

      Reply
      • thank you for your reply, yes what you said makes sense, let me answer some of your questions to make it more clear, in the master bedroom the airflow is strong and cold, the room is usually cool, in the other 3 rooms it varies, the airflow gets less and less, for the room above the garage it is usually very hot, and actually in the upstairs bathroom (not the master) there is barely any airflow and the bathroom is usually very hot. So i think like you said the problem is either with the attic, or the dampers. if you have any more suggestions let me know, the rooms are very close to one another btw. i will surely need to get the AC checked by someone. thank you

        Reply
        • Yes, Mike, it sounds a bit like maybe some of these rooms were part of an add-on (above the garage, maybe?) and that original ductwork that was meant to serve 2 or 3 rooms now serves all of them. By the time the air gets to the far end, there’s nothing left. You can try using the register baffles to slow delivery at the front end, but that may not help much. A system of zoned heating dampers might help, depending upon the ductwork configuration. See http://www.hometips.com/buying-guides/zoned-heating-systems.html for more about this.

          Reply
    • Mike,

      I have same issue with AC in my home.Bottom floor works fine and top floor has issue day time.
      Top floor temp raising to 80 during day time though I set for 72 and no Issue during night time.

      What did you figure out with your top floor AC ?

      Reply
    • I am curious as to the location of your return air in the upper part. The room you say is cooler may be where the return air duct is located and just pulls the heat out of that room and not so much the others. Return air placement in a two story home is very critical, and some home builders my take a short in put them in the most affordable place. Keep it in mind that hot air rises and cool air falls so the down stairs unit should not be working hard at all.

      Reply
  98. Please see “Air Conditioner Does Not Cool Well” in the article above. Other possibilities are that the condensate drain is clogged or the thermostat isn’t working right. Or, if the system is pretty old, the refrigerant may need to be recharged—something a pro must do.

    Reply
  99. We have an older central Heat Air Conditioning system. When we turned it on this year it ran a couple of days then quit cooling. We open up the inside unit and discovered that the A/C coils(?) were frozen over. We thawed everything, replaced both the filters, and swept out the upper unit. We turned the unit back on and it worked another couple of days and the same thing has happened. The A/C coils (?) were again frozen over. Any suggestions as we are financially unable to replace the unit at this time and we live in south texas so really need some kind of cool air. Thanks a lot for any help

    Reply
    • Sounds like it’s low on refrigerant. Another possibility is that is not moving enough air across the cooling coil. Ex. dirty blower wheel blades, or worn fan belts, it they exist. You say you swept out the upper unit, so I take that as meaning you can get access to down flow side of the cooling coil. You probably need a service tech. It’s not healthy on the compressor to send un-boiled refrigerant back.

      Reply
  100. We just moved into our new home tonight to find some sort of problem with the ac. The home has been vacant for about 9 months for a remodel. when we moved in tonight I tried to turn on AC and we got a little bit of air (not very cold) coming out of the vents. All of the breakers are good, and everything’s fine as long as I can tell. The outdoor unit almost doesn’t seem to have any power going to it and the fan doesn’t spin. I tried turning it to “kick start” but it still doesn’t work. It’s about 85 inside and really really humid. Please help!?

    Reply
    • Ryan, the outdoor unit is probably connected to its own electrical sub-panel box with a breaker (sometimes a handle). Make sure it is powered on.

      Reply
  101. Our AC unit is in the attic and cutting off power recently. When we turn the power switch off and on it works for a while and does the same thing again. Thank you for help.

    Reply
    • Are you saying that it keeps tripping its circuit breaker? If so, it could indicate an electrical problem that should be looked at by a pro. But first make sure the unit has good air flow—clean or replace filters, etc.

      Reply
      • Thank you for your answer. We did replace the filters. It worked longer but then it happened again. We will check for electrical problem.

        Reply
  102. My thermostat would go blank and after I would take it off and put it back on and push some random buttons I could get it to come back on. This worked 3-4 times, but now it’s been out for 5 days and I’ve checked everything I know to check. All the breaker switches are on: fuse box, on the unit itself, the furnace (though I definitely don’t need it…live in the South), outside by the compressor. All on. The thermostat doesn’t take batteries. It doesn’t have a drain pan and the drain tube is clear. The thermostat is only a year or so old and still under warranty so I called my HVAC guy, but of course he’s out of town and can’t get to us until the upcoming week! The last 4 days were tolerable bc it’s been overcast and raining, but today it’s nice and sunny and we’re dying over here!

    Is there anything else I can check? Oh…one more thing…before it died from the inside it would sound as if the unit was slowing down/cutting off but then it’d pick back up again. (Like the AC or lights would do in a car that has an alternator going out).

    HELP?!?!

    Reply
    • ChiChi, by the beginning of your post, it sounds like you have a faulty thermostat. Are you SURE it doesn’t have batteries? Considering the urgency, if I were you, I’d be tempted to buy a replacement …and see if the AC guy will cover the cost when he returns. I don’t know what to make of the last part of your post.

      Reply
  103. My air stopped working. I opened it up and the blower motor was humming. I reached in and started spinning it by hand and it slowly got up to speed. Later it did the same but it took longer to get running and when it did run it was not full speed. Any ideas?

    Reply
    • The run capacitor is not working. It’s a canister that should be near or on the fan motor. Replace it and should be ok. Do it soon or the motor will be damaged.

      Reply
  104. Is there some sort of low air-flow safety switch to prevent the fan from coming on? (I need to replace the filters.) The outside unit runs and moves coolant into the coils but the fan is not coming on. Even when I turn the heat/cool to off and the fan from auto to run, there is no run. Any ideas?

    Reply
    • Check for a door switch on the air handler. If the door is not shut correctly, it will not allow the fan to run.

      Reply
  105. I have a Revolv air conditioner. This started after winter when days were hot and nights cold. We would switch from heat to AC, but it wouldnt come on. We would have to throw the breaker and wait a few minutes then turn breaker back on and air would run. The power went out the other night and when it came back on it felt as if the heat was running. We threw breaker and back on and air ran. Few days later and now air runs all day then starts blowing hot air, but throwing breaker doesn’t fix. AC repairman unhooked heat and straight wired but last night started blowing hot air again after being cold all day. What can it be?

    Reply
  106. What is the problem if it seems like everything is running except no cold air coming out of vents inside? And we just used it earlier in the week and worked fine….

    Reply
    • Please read “Air Conditioner Doesn’t Cool Well” above and let me know what you have or have not done. Need more info.

      Reply
  107. My apartment air conditioner has never cooled like it is supposed to. it has been on most of the day, today, and I am sitting here typing this sweating. I’ve called the landlord, and they’ve sent someone, but every single time. “Oh the room won’t cool because your curtains arent blocking the sun in the living room properly”, or “the compressor was bad, I replaced it” you can replace a compressor in 30 minutes? “you’ve got full levels of Freon”, and at that particular moment, it was blowing cold air. hour later it’s 80 degrees in my apartment. I feel like my landlord wants me to move so he can raise the rent higher for a new tenant, I can’t really afford this as I am also a caretaker fr my aging grandmother. this heat is not good for her nor my animals. any ideas? I thought of getting an outside person to have a look, but they would need the landlord’s permission. at this point a rotating fan is cooler than what my unit is doing. I checked, it’s not frozen up, it has a brand new filter, and it is leaking drops of water and making a hissing noise as if it’s actually working, but there is no air coming from the vents. any thoughts?

    Reply
  108. Our central air stopped working… the unit was running, but fan wasn’t spinning. Had someone come to diagnose/fix: New motor and capacitor, all seemed well… But, it worked for one day and then the same thing happened again! Called HVAC guy back, he returned and told us NEW motor was now burned out! So he re-diagnosed, and then returned with another motor and “disconnect,”hopefully to fix it once and for all. But… Now he says the motherboard is fried! It was smoking when he was working on it today. Seems to me the professional made it worse…. it was NOT smoking before we called him! Any insight as to whether this guy is incompetent, or are we just unlucky??? When he “fixed” it the first time, he never said anything about there possibly being an underlying cause. We are trying to figure out if we should let him complete the work or just cut our losses and call someone else. Thanks!

    Reply
    • Seems to me that, if both the motor and the capacitor needed replacement the first time, they probably fried from some kind of electrical surge, which the HVAC guy tried to solve with the “disconnect”…sound right to you? I’m not sure why the motherboard was fried after the disconnect was installed. I don’t have a good feeling for the guy’s competency. I’m concerned that he replaced the motor without diagnosing the reason the capacitor and motor fried in the first place.

      Reply
      • Thank you; exactly right. After some arguing with my husband, he ended up calling in a “senior tech,” who confirmed that the guy screwed up by not fully diagnosing the problem… long story short, it’s fixed now, and we did not pay for the new motor! Thanks for your reply. =)

        Reply
      • I find that through my career, many refrigeration tech’s are not trained as competent electricians, or they would probably be electricians. So troubleshooting the root cause of burn outs require a good understanding of electrical circuits and using metering competently. Not knocking them, but it takes many years of experience and training to master both the electrical field and the refrigeration field. Ex would be that most AC companies are also plumbing companies. Electrical contractors are not prevalent in the air conditioning business. Just my two cents worth.
        Bottom line. Call another tech with hopefully more years under his belt in troubleshooting.

        Reply
        • Thank you, Pat. Well said. I totally agree.

          Reply
  109. my air was working fine till about three days ago. I know it is getting hotter but it hasn’t got that much more in less than a week.. I called a repair man and he said it was my out side coils corroded . my unit is only three years old. how could it be that. wouldn’t my unit have been acting up before this week. it was 95 outside and it was 80 inside. The repair main said I needed a new outside unit help me its only three years old

    Reply
    • Sounds pretty questionable to me. The compressor should be good for many years. Check your warranty…a Trane or American Standard compressor, for example, probably has a limited 5-year warranty. Carefully read through the “Air Conditioner Doesn’t Cool Well” section above, and then read through this discussion forum…there is a ton of solid information that will help you solve this. Before replacing anything, get another opinion, but don’t tell the HVAC pro what the first guy said.

      Reply
      • Called another guy. Condensate line was clogged It was 87 in home yesterday now it is at 5 pm 75. AV set on73 and is well in th90s outside. Shouldn’t the unit cool to what it said on

        Reply
        • Don’t know the time span you are talking about. Once your AC is working, it has a very hard job to remove the moisture in the home. Could be hours. Once the moisture is gone, and the air is dry, then the AC works much faster.
          There are so many hacks out there taking advantage of folks by giving you false diagnosis just to take your money. Always call a company you trust or a company that looks professional when they reach your door. I mean uniforms, Id badges on their uniforms and a clean service truck. Not saying there aren’t some good qualified folks out there that can’t afford all that yet in their business, but just be careful when selecting anyone your going to pay out a lot of money to.

          Reply
  110. Air conditioner went out today. It won’t kick on at all. Not sure how to check fuses, but I’ve done everything else so far. Tried touching Y terminal with R and got a buzzing noise from the outside unit. Any idea why?

    Reply
    • The buzzing noise was more than likely the contactor engaging in the condensing unit outside. Sounds to me like it either kicked out a circuit breaker, or blew a fuse. Check all your circuit breakers in your panel, and also check for an outside disconnect near the outside unit, and look for any fuses in it. Be careful around electricity and turn off any switch’s before pulling fuses. If in doubt, please call a repairman. Better safe than sorry

      Reply
  111. Central AC stopped cooling today. The fan on the condenser is blowing but the compressor isn’t working. About every 5 minutes you can hear a buzzing coming from the compressor, it lasts for a few seconds and stops buzzing. I have been hearing this buzzing noise off and on for several weeks, but the compressor would kick in and then it cooled fine. Does the capacitor also control the compressor? I had to replace the capacitor about 6 years ago because the condenser fan wasn’t turning.

    Reply
    • Sounds like the capacitor that run/starts the compressor. Many of these capacitors control both the fan and the compressor. Replace it and should be ok. Make it soon or your compressor start windings will burn out.

      Reply
  112. The central a/c for our small house is blowing with minimal force out of the largest duct (the one that requires a filter). Air is coming out of the smaller vents. Outside compressor seems to be working. In previous summers, if one stood below the filtered duct, you were hit with a blast of cold air. Now you can barely feel the air flow. Also: the control says to Service Filter, though I have changed it a couple of times. Any ideas? Thank you.

    Reply
    • I am confused about air blowing our out of the filtered duct. There should not be any air blowing out of that. It is an air intake to the air handler, or furnace. Sounds like some kind of an air blockage to me.

      Reply
  113. Colman heatpump. Outdoor unit does not run.Unit will run if contactor is manually closed replaced defroster pcb and thermostat, no help.

    Reply
    • Check your condensate pump on the inside air handler. If the pump doesn’t work and gets full of condensate water, it will shut down your compressor unit. Check for the door switch on the furnace. The control transformer in the air handle, ( furnace or attic air handler). If you changed filters, maybe the door didn’t shut correctly and this will shut control power off as well. Also the contactor in the outside unit may be faulty and not picking up. Try these items. It is a 24 volt control issue. A meter would really help, but be carefull as there is high voltage in the outside unit. (240 volts)

      Reply
  114. My AC seems to be working ok (I had it checked and the compressor replaced in the Spring), however I live in a multi-story townhouse and it is not blowing through the lower level vents, and only select vents upstairs. Wondering if this is an AC issue, or a duct work issue?

    Reply
    • Replacing the compressor should not affect the flow of air. Sounds like a zoning issue. How many thermostats do you have in your home that control the air conditioner?

      Reply
  115. I use a split air conditioner
    When I put it on through the remote
    It doesn’t come up immediately,
    The digital panel on the indoor unit flashes on and off for a couple of times
    If it manages to stay on and work, it switches off again by itself and I have to battle the remote to switch it on again
    Pls what could be wrong ?

    Reply
    • Most units, or the thermostat has a 5 minute delay before turning the compressor on. This is to prevent the compressor from starting under high refrigerant pressures after running.

      Reply
  116. The system works, but no cool air. A AC repair guy wanted about $1400 to run a leak test on a old unit and fix it. I said no. Another wanted $160 to run a leak test but told me if it is in the coil you need a new one. Should I just keep contacting these AC repair guys , run the test, or get a new unit.

    Reply
    • I think you live in an area that is full of rip offs. In my day, finding and fixing the leak was part of the job to replace lost refrigerant. Time and material was the cost, no a separate charge to find the leak. It sounds is if you would pay the charge for finding the leak, and another charge for fixing it, and yet another charge for recharging it. I would keep looking and pinning them down on the phone as to how they charge you. Is it a separate charge for each phase, or simply time and material for the complete repair. Where do you live that has there people that charge like this?

      Reply
      • Pat, I totally agree! Thanks for answering this.

        Reply
  117. Outside fan on ac unit running but inside thermostat says filter. I looked down thru fan turning and I see snow on pipe or something…

    Reply
    • You need to check and/or change the filter of the air handler. Either your furnace or attic air handler. If it’s in the attic, the filter should be in the return air grill, probably in your ceiling. The ice you are seeing is due to not moving enough air through the coils in the cooling unit. If not corrected, it will eventually damage your compressor.

      Reply
  118. goodman cpkj24-1a had tech out last week, replaced starter cap and added 2lbs of coolant. unit worked two or three days, now condenser isnt kicking on. is it shot? husband does controls for a living wants to check the lps but cant really find anything helpful so far..HELP

    Reply
    • Possible overcharge of refrigerant. That will cause high pressure in the compressor and a sensor will shut it down to protect it. Also, If a refrigerant charge was needed, did the service man find the leak and repair it, or just add refrigerant and the system leaked it out as well. You need a technician you can trust and make a complete repair instead of just making it run for a while and charge you again in a few weeks. If it was overcharged, then you may have a fuse or a circuit breaker for the outside condensing unit tripped.

      Reply
  119. Unit was making a noise. After looking at it I noticed the fan blade got bent and was touching the side and not moving at all. Should I try turning it on to see if the motor still works?

    Reply
  120. i live in southeast texas and has been hot,my central a/c unit does not want to shut off,i have thermostat set at 82 and it just keeps running,have replaced batteries in thermostat and in the evening it seems to cycle on and off much better.i also have a problem with a lot of condensation on my condesor coils in acctic,their is alot od dripping of watre into pan and it all seems to be draining out of the overflow pipe,not the main drain pipe connected to condensor

    Reply
  121. Thoughts or ideas if you dont mind.

    We live in north florida and have a Payne unit. Currently the temp is set to 74° but the temp in the house is 82°.. and the unit is not running. It runs periodically when it wants to.

    We’ve had a company come out twice already and they cant explain it or find anything wrong with the unit or indoor air handler. When its running its blowing cold air but never enough to cool the house or maintain temp. It wont return to 74° in this house until 3 hours after sunset tonight.

    We didnt have any trouble the previous 2 years and as i said nothing appears to be wrong. They did put the fan speed on high to attempt to push more airflow but it hasnt helped.

    We dont mind paying if somethings wrong but the unit is 2 years old not keeping up for no apparent reason.

    Thanks and i look forward to your reply

    Reply
    • If the company you called can’t figure out what the problem is, then that company is not qualified. It sounds as if you are low on Freon, but there are many other issues that needs looked at. I always suggest to take the temp of the ambient air in the house, and the temp of the nearest discharge duct and look for a difference of 18 to 20 degrees. If it is not close to that differential, then there is an issue with either Freon charge or air moving issues. It sounds to me like it is possibly low on refrigerant and cutting off on low pressure. May other things to look at, but that will be a good start. Find yourself a good technician. Any service man that tells you they cannot figure out the problem is not qualified.

      Reply
      • Pat, checking the temperature difference sounds like something I need to add to the article. Thanks!

        Reply
        • That’s the rule I always used. It may not be exact, but close enough for a goal to reach when tweaking a system. It would be nice if you were to feel confident in those numbers and add them, and I will not have to sound like a broken record with most posts. I am curious if other tech’s use this number, or if they don’t agree. Thanks Don.

          Reply
      • My apologies on not getting back to you. The issue turned out to be a simple fix. We have no attic space and the closet the air handler room is in was over 100 degrees during the day. We insulated the closet from the top of the doorway and no more problems. We had just removed 30 large pine trees from the yard during the spring and it looks like they gave us more shade than we thought…. however it wasn’t the technician that solved the issue. It was my girlfriends dad who ultimately figured it out. Thank you :)

        Reply
  122. Our ac fan was not spinning so we had capacitor professionally replaced. Even though air is cold coming out of vents, there is almost no air flow at all, as if set on low and prior to this was set on high.
    We have changed the filter, cleaned the coils, reset the system a few times, and looked for a low with high switch on the a/c unit, there is not one. What else can be causing almost no air flow out of the ducts? When it is set to only the fan setting, there is strong air flow, but when set to cool and the outdoor unit kicks on, there is about 20% air flow. It was not like this prior to yesterday when the capacitor failed.

    Reply
    • Perhaps he put the wrong fan motor in. There are different speeds and it may not be set to the high speed needed for air conditioning. You furnace will run on a lower speed in the winter as hot air is easier to move than the heavier cold air. Have your technetium check this. Although he should have checked it to begin with. Take the ambient air temp in your home and take the air temp coming out of the closet vent to your ac. There should be between and 18 to 20 degree diff. No more and no less, within reason. Too clold means your blower is not moving enough air. Any warmer means that there is too much air across the blower. There could be other issues involved, but this is the first thing to check.

      Reply
  123. My ac is not cooling enough. We assumed it was because the inside unit was dirty because we could see dust on it. Repairman sprayed with coil cleaner and brushed dust off. Still didn’t cool well. He came back and checked freon and pressures. Pressure was off, so he thought it was the compressor. Changed compressor and dryer, filled with freon. No improvement. Will keep up at night, but not during the day. Pressure still shows to be off.

    Reply
    • You need another service tech. This man evidently doesn’t know what he’s doing. I have seen, over my years in the business, so many compressors replace by misdiagnoses. They will never admit it. Don’t ever have a compressor replace without a second opinion. This man ripped you off due to his lack of ability to trouble shoot, at your expense. Get another tech. period.

      Reply
    • Any technician that tells you your compressor needs to be replaced should also be able to tell you exactly what cause that compressor to fail. Especially if it is less than 10 or 15 years old. I have never replaced a compressor unless I knew what caused it’s failure. There will always be a root cause that will simply take the new compressor out sooner or later. This is called being an experienced and well trained technician. If he can’t, then call another tech. My advice to keep you from getting ripped by an unprofessional tech. Compressor replacement is not cheap so make sure you can depend on your tech. With this heat wave, the fly by nights are crawling out of the woods.

      Reply
  124. My central air is doing everything except blow out cool air what is most common problem?

    Reply
  125. Just clean the coils. I turned my unit off at the outside box now it will not turn back on has anyone else had this problem?

    Reply
  126. Island Air Conditioning Split unit it is it was built in 98 and still runs it’s nice and cold but not freezing but it’s cold it runs but it’s leaking water everywhere water is being blown from the blower on to the floor and not into the drip pan I’m not sure what to do if it’s been thoroughly cleaned it’s been maintenance by a guy then they told me it needs Freon which is $700 to just do that on top of the thousand dollar maintenance they did to it did not fix the problem which it didn’t fix the problem cuz it’s still dripping all over my floor it still drives it still works everything works but it just drips onto the floor I don’t know what the problem is another guy told me I need to replace the system I’m not sure what to do any suggestions would be appreciated

    Reply
    • If it’s cooling, and not forming ice on the lines, then it should not need Freon. Take the temp of the amibient temp of the room and the temp of the air closest to the AC discharge air. It should be 18 to 20 degree difference. That will tell you if the AC is working right and the problem is in the waer removal. I would get another opinion. the water channels in the cooling coil section is not clean. it will make a lot of water on hot humid days and the water channels in the evaporator, *the cooling coils) is directed either to a drain or a pump that takes the water to a drain. The prices you quoted, to me, is extremely high, but that may be the going rate in your area. For the money you are talking, I would get another tech from a reliable company for their opinion.

      Reply
    • Jen, please see the info in our article about the condensate pump. It sounds like none of the condensation is being properly collected and pumped out. I agree with Pat, below, about talking to a different AC pro.

      Reply
  127. My brother is,saying the compressor is cutting off before the house reaches correct temperature???

    Reply
  128. After working just fine, suddenly Ac unit oitside goes on fine but after about an hour shuts down. Initially noticed outside unit running but fan not turning. After a day of non use unit started fine but now shuts off. Any suggestions please?!

    Reply
  129. I have a multi zone unit. Every few weeks the inside unit will stop running. I have to turn the power off, and on. It will run again. I don’t know what is wrong. The AC company told me I have to change the whole inside unit. Anyone can give me some suggestions?

    Reply
    • Get another opinion
      And they should explain why it needs replaced because it makes no sense to me unless you can give more information as to the need for replacement. It could be just short cycling due to the zones calling for cooling at different times and not letting the compressor equalize pressure before trying to restart. Just a thought. Need more info.

      Reply
  130. I hit this coolant line with the weed whacker and lost my coolant. Any idea on cost to repair refill?

    Reply
    • Depends on the going rate for your area. Beware of rip offs. The damage will have to be soldered shut, the system dehydrated, possibly a new filter/drier, and recharged. A couple hour job. I would defiantly get a couple quotes and make sure they are from a reliable company, and not one of the fly by nights running around. Don’t look for cheap when making your choice. You may find a drastic difference in prices. Look for a successful business with qualified techs’ and the repairs will last.

      Reply
  131. We purchased our home last November so this is the first summer we have used the AC. When we first turn it on, it blows cold air. After about an hour, the air is warm. The house temp will go from 72 to 74. When I turn off the unit the temp will drop to 73. We will wait about an 1/2 hour and turn it back on and it is cold again for a short time. I have had a technician come out and he has topped off the freon, checked for leaks and says it should be fine. We had a friend suggest we check the damper to see if it was open (they had a similar problem and this fixed theirs). We could not find a damper on our unit. Any suggestions?

    Reply
  132. I have a 2009 Trane XL16i – outside fan is running, air handler is running, air being blown in the house is warm. Compressor is NOT running, but the fan is…is it still possible that the start/run capacitor is bad if only the compressor is not running but the fan is?

    Reply
    • Read the above troubleshooting guide. Don covers that topic real well. Be careful working with high voltage on the contactor. Turn the power off and check the contactor for welded contacts. This is a common problem.

      Reply
  133. Hi This is my 1st summer owning this house. My electric bill has been doubling for 3 months in a row..I have a Carrier 25HPA6 Performance Series 2 Stage Heat Pump…I recently went online and found instructions on how to clean the outdoor unit. I did so and it was not very dirty. I also have a generator that kicks on when I lose power which does not support the AC unit..We did lose power for a few days recently. I have 2 faults showing on the heat pump unit..one being 53 outdoor air sensor not reading or out of range 255 events and F 37 control fault, heater stuck on 13 events. I have never had a heat pump or central Air and am very green to this. PLease help?

    Reply
    • You need to find a good tech. It may be the your electric heating strips are coming on due to that defective sensor. It may think it needs emergency heat and maybe even trying to defrost. A service call may be less expensive than the electric bills.

      Reply
      • OMG! Had a service tech come out yesterday and bingo the heating strips are stuck on and the tech is going to check on the cost of a relay switch and get me an estimate..Was well worth the $89.00 diagnostic fee. Any idea the cost to fix something like this. Thank you for your insight Pat McBride! I appreciate it. Last month the electric bill was $330!!!

        Reply
      • Is a sensor the same as a relay switch? That is what my tech thought was the problem causing the heat tape to be stuck on. Is it a costly repair? You are genius. Thank you very much. BTW my electric bill jumped to a whopping $330 last month which surely caught my attention.

        Reply
      • Am I supposed unplug the heat tape when no longer needed for the season? Is there anything to do to the ac before winter?

        Reply
  134. Hi. Downstairs AC blowing cool, but not cold and less pressure than usual. Fan outside is spinning fine, but the air coming out of the outside unit is cool, while the air coming out of the unit for the upstairs AC is warm (which is what I think is supposed to happen). Why would the air coming out of the outside unit be cool? Does that give any clues as to why the AC downstairs isn’t cooling as well as it should be?

    Reply
  135. My central air is not working right, we have it set on 72 and in the early morning it blows out cold air but after it gets warmer outside, it doesn’t blow out cold enough air, it comes 79-80 degrees in the house, had it checked, said it had enough freon

    Reply
    • Take a real close look at the condenser coils on the outside unit. Probably dirty making it inefficient during the hotter parts of the day and will work better at night when it’s cooler outside. Check them very closely as with fine fins, they can be hard to see through. Use a flashlight if you have to. You want to see through them very clearly all the way up and down the colils

      Reply
      • Pat, once again…thank you very much with helping answer these questions…your answers are great!

        Reply
        • Thanks Don. I miss the business of trouble shooting machinery. I was also an Industrial electrician for about 40 years working with machine automation and PLC controls and supervised foundry maintenance departments for 20 of those years. Just let me know if I step on your toes in any way. Just having some fun here. .

          Reply
          • Hello, my central air unit runs, but is only blowing out room temperature air. It won’t get cooler than 84-85 degrees in the house. It was working fine before then. Any suggestions? Thanks!

  136. My air conditioner is not cooling. The heat does work. I turned it off for a week while on vacation. It was working before I left and would not work when I got back. I have been told that it has plenty of charge…the guy said it was the compressor…I’m not so sure. I have replaced the thermostat, start capacitor and hard start kit. I have power on all 3 legs of the compressor. Ohming the compressor leads are: C to S = 1.5 ohms, C to R = 4.25 ohms and R to S = 5.5 ohms. All three leads are open to compressor case. I let it run all night. In the morning, top of compressor was slightly warm, but easily touched. All 4 lines coming off of the reversing valve were slightly cool to touch. Any thoughts?

    Reply
    • Call someone else. How can the man say the charge is correct and in the same breath say he it could be the compressor. That’s silly. A heat pump is very complicated to trouble shoot electrically concerning the controls, not the pump necessarily but there are lot of things that can go wrong with the controls If I was to guess, I would point at the reversing valve that changes it from heat to cool and defrost. Those are common to fail. Call a heat pump tech. By the way, those are good ohm readings Any bad readings and the pump will not run. If there is an issue with the compressor (pump) it would more than likely be in the valves and they are easily tested on a heat pump.

      Reply
  137. I just moved into a new townhouse apartment last week. I live near the beach in southeastern VA and it’s been in high temps here so while my dad was helping me move, he turned the thermostat to “on” and to 65 since it had not be on for a few days and was really hot both inside and outside. The next day I noticed a leak in the ceiling in the downstairs bathroom. I reported it to maintenance and when I returned home there was note saying I had the temp too low and needed to set it to “auto. i completely forgot to change it back with everything going so I immediately set it to “auto” and 68 (my norm). 2 days later and I get another note from the maintenance guy saying I need to keep my AC on auto and set between 73-75. Yeah right, it is at least 5-6 degrees hotter upstairs. So much so that I can hardly sleep and that’s if the temp is on 70. I have to dry and style my hair downstairs in the living room due to the high temp and humidity upstairs. I was raised in a cold house and I cannot sleep in a hot room even with my trusted powerful box fan on high blowing right on me. Yesterday I turned the AC completely off for a good 12 hours while I was gone and the ceiling is still leaking. And, you can tell they’ve fixed it before by looking at it. It’s gotten worse actually. i now have my temp set to 68 so I can sleep somewhat comfortably soon and it’s steady leaking. What is causing this? I’ve always lived in older apartments on the top floor and never had this issue before. I’m used to paying high electric bills due to the heat rising and having to combat it. If I had known there was an AC problem or temp issue before I signed my lease, I never would have. This all makes me so sad. Please help me!

    Reply
    • Your ac will condensate more at higher temperatures than lower as it removes the humidity as it cools, so the cooler the air, the less humidity. Your maintenance people are not looking at the real problem If the moisture is coming from your ac, it’s either because the air handler is above the leaking ceiling and the condensate drain in not working, or the duct work leading to the upstairs is not insulated. Or there is a plumbing leak. If you are tied to a long lease, you may want to hire a contractor to determine what the issue is and pass it on to your apt manager, and ask to be reimbursed. You may have a contract that forbids this, so check out the legalities. But the maintenance folks are on the wrong path IMO

      Reply
    • Jennifer, it sounds to me like the AC unit is producing a lot of condensation, especially when set to lower temperatures because it runs most of the time when set that low. That condensation needs to be pumped out of there with a good condensate pump (or the drain lines need to be cleared).

      Reply
  138. My AC works fine overnight and during the morning, but by late afternoon and evening it comes on from time to time, but not enough to get down to the 77 I have it set for. By the time I go to bed it is up to 83 or so, but overnight it starts working fine and by the time I get up it is 77 again (we live in Florida and outside temp is still in the 80s overnight). Had the AC checked and they say everything is fine, but for at least 3 weeks, it doesn’t work right and the evenings get warm. Any ideas? I live in a small, 1,000 sq ft condo, with my own compressor and air handler.

    Reply
    • Check your condensing unit. I think it is dirty and not moving enough air to cool it. Look at both the inside an outside of the coils. Take a flashlight and hold in on one side while you look through from the other side. I feel I am safe in saying your condenser coil it plugged. It’s cooler at night so the unit will work a bit better. Let me know if that is the problem please.

      Reply
      • Check or replace the fan capacitor. If the capacitor is faulty or below capacity, the fan doesn’t turn fast enough to cool the hot condenser coil.

        Reply
        • I believe that if the fan capacitor is bad, the fan motor would not run, cycle on and off, or burn out after a while. Another possibility would be a low refrigerant charge. Enough to cool when the load is lighter, but not enough to cool during the heat If it;s a thermostatic controlled refrigerant valve, then it has an accumulator to store excess refrigerant and release it when the demand is higher.
          There are several possibilities. Would be nice if Rob were to let us know what was found. Just curious

          Reply
  139. My fan out side spins when you turn it on but then stops hums and the motor gets really hot. It this the compasitor?

    Reply
    • Yes. I do believe it is the capacitor. It may be a duel capacitor that also starts the compressor. Make sure you get an exact replacement and safely turn off power before attempting any repairs. Also test to make sure the power is off. You may want to call a tech for this unless you feel safe in taking this on. Maybe you have an electrician friend.

      Reply
  140. My ac fan kicks in and spins for about 30 seconds but does not flow air into the house then fan shuts off. It Keeps trying to come on every few minutes but does same thing repeatedly. Please help!:/

    Reply
    • It could be the motor run capacitor, or just a failing motor. You need to check the filters, although I don’t believe that would necessarily be the problem, but check the filters anyway, then call a dependable HVAC company or an electrician friend to check the run capacitor for the fan.

      Reply
  141. Had a storm come through last night didn’t seem bad at all but the electric went off and came back on 4 times rather quickly. After the 3rd time I shut off most everything in the house, including the central air. After about 30 min of the power staying on I turned the air back on. It kicked on and seemed fine. A few hours later when I was headed to bed I took notice to it being rather warm in the house. There was a 4 degree difference in the room vs the thermostat setting. Went down to check the unit, looks like it was starting to freeze up. Pulled the one filter out and it was wet. Came back up shut it off and have been wondering what to do, if there is an easy fix I could try before I call someone.
    I read somewhere online to turn it on but just the fan not the actual a/c. Is that all it might need or do you think the power going off and on quickly fried something?

    Reply
  142. Would love to get your opinion on my recent Ac issue.

    Just purchased a new home last winter which had a brand new ac cooling unit installed, it has worked great all summer up until I woke up this more, hearing a weird buzzing/clunking sound, I check the thermostat it was set a 73 but room temp was 75, the furnace blower motor was not running so I went out back and the sound was coming from the cooling unit. So I turn off the whole system waited for a few minutes, turn it back on and same results. I notice lots of condensation coming off the cooling lines like I have never seen before, it’s like the condenser is running but nothing else. I am now just running the furnace fan by itself just in case the system froze up.

    Any other thoughts for trouble shooting?

    Reply
  143. The fan on my central air unit outside quit working. I did spin it by hand. It did take off just not as fast as before and got very hot. What do you think my problem is?

    Reply
    • Have an AC tech check the fan run/start capacitor. Please let us know what was found to be the problem.

      Reply
  144. outdoor unit fan is running but the compressor is not running. It is not buzzing or making any sound. The contactor is working. I had the coil replaced in the winter- is it possible the winter repair had a leak and I lost the refrigerant?

    Reply
    • The contactor also runs the condenser fan. Replacing the coil would not affect the refrigerant charge either. It is possible to have a leak aside from the repairs. It’s also possible that the compressor motor has burned out. You need an electrician fan to ohm the motor and trace the power to see where you loose it. Best off to call a good AC tech to also check the R charge. Good luck and let us know what was found please.

      Reply
  145. I have one unit, two thermostats, air is working but does not maintain the desired temperature. The upstairs intake is sucking well, the downstairs intake is not. I feel now air coming out of vents. AC Guy was here last week and replaced a pressure valve on the outside unit. This problem seems to be going on since then. Could it be related?

    Reply
  146. Outside AC unit relay keeps making a clicking sound and the AC is not blowing cool.

    Reply
  147. I scanned the q&a here and didn’t really see exactly my problem, so here are the details:

    1. The AC mostly works. Good, right?
    2. Sometimes (always in the evening) it turns off, but not at exactly the same time. 7 pm to 9 pm, sometimes not at all.
    3. When it turns off, the condensate trap pan is dry (so it doesn’t appear to be the automatic flood off switch.) When it is running there is a steady normal drip down the condensate drain outside. I have two air conditioners in the house, and the outflows appear the same.
    4. If I wait a while, I can turn the AC back on and it works.
    5. I checked the schedule of the unit and the cool temperature (we keep it cooled to 78 F) is the same.
    6. The refrigerant line is cool to the touch, identical with the unit that is working fine.

    Any help would be appreciated. I’ll look for more clues tomorrow.

    Reply
    • I’m not understanding what your complaint is. Does it cool ok when it runs?

      Reply
      • Thanks for your reply, Pat.

        My complaint is that it’s not supposed to turn off. ;-) We washed the outside unit, made it perfectly clean, drained out the pipes again, and tested the refrigerant levels (they were ok). So far, it’s still working.

        Reply
  148. central outdoor air cond. has power to the unit but will not start. no sound at all coming from unit. bought new thermostat still nothing. checked for loose wires.

    Reply
  149. We just had a brand new carrier unit inside and outside put in 1 week ago, we have it set To 75. It gets to the 75 overnight, but as soon as the sun comes up my thermometers In different parts of the house rises to 78. It stays at 78 all day . I’m sure sometime after midnight it gets to the 75. Why doesn’t it maintain the 75 all day? I’m afraid to cook and heat things up.

    Reply
    • You need to get back with the installer, sales company. It may be possible that it’s undersized. When the temp starts to rise, check temp in the home, and the temp coming out of the nearest discharge register to the furnace. Should be approx. an 18 to 20 degree diff. Let us know.

      Reply
      • Pat, thanks so much for helping out with all of your expert answers!!

        Reply
        • Thanks Don. I miss the trade and enjoy the challenge. It would be nice if folks responded more to let us know it we’re on the right track. It sharpens our skills as well. Not always right ya know. Imagine that.

          Reply
          • Hey People, you have a real expert here in Pat. When he helps you fix your AC issues (or if his answers don’t quite work), please jump back onto the site and let us know!

      • Thank you. We Did call the installer they sent a different technician out. Their was a wire either loose or not hooked up properly. Now we can actually hear the unit running in the house where before it was so quiet you couldn’t tell it was on. I knew something was wrong. Thank you.

        Reply
    • This one is hard to diagnose from this information. Different rooms will read different temps, depending upon exposure to the sun, etc. Make sure your AC’s thermostat is set properly. Sorry I can’t be more helpful.

      Reply
  150. I have a black n blue wire not connected were does these wires go

    Reply
    • Not enough info. Where are these wires located? Are they small solid wires? Some thermostat wire cables have more wires in the cable than is needed, Have they been stripped back to show the copper? You have to be more descriptive. Does the unit work? Get back with us.

      Reply
  151. When my central unit reaches desired temp. the unit keeps running and blows warm air, and does not go to off position.

    Reply
    • Check to see if the fan setting on the thermostat is set to on, or auto. On runs the fan continually, auto runs the fan when the AC, or furnace is calling for heat or AC.

      Reply
  152. Hello, I hope you can help me. My problem is becoming more frequent. My unit works fine for a few days and then all of a sudden I notice that the house is getting warm. The outside unit (compressor) is running but the inside unit is not. The lines and coil freeze up solid. I turn off the breaker, let it melt and turn the breaker back on, and all is good for a few more days. This started a while ago and was originally happening only every other month or so but has gotten worse. I should note that I have caught it a few times before it was all frozen and a breaker on & off fixes it every time. My unit is a 7 year old Trane with a variable speed fan motor. I have also started hearing a hum from a transformer on the inside unit. Thanks in advance for your help.

    Reply
    • That transformer hum your hearing may be a fan relay. Depending on the type of unit, there is normally no transformer in the air handler. You say you noticed the outside unit, (condenser) is running, but the inside fan is not, and you have a variable speed fan. This is where I would suspect the problem to be. The variable speed controller may be causing the motor to run too slow causing the gradual ice build up. Resetting the breaker may be resetting this controller. You can bypass this controller and have you fan run full speed continually. This will isolate the problem. Make sure the return line is flashing cold and sweating when it’s running to show that the refrigerant charge is adequate. This can also be determined by taking temps of the discharge air from the register closest to the air handler. There should be a 18 to 20 degree difference. It may be a bit low on charge and cause the icing up as well over a period of time. I would appreciate letting us know if any of this makes sense or corrects the problem.

      Reply
      • I think I figured it out. The fan inside was not running at all (not even at low speed) and it would ice up quick. Turning off the breaker gave it time to defrost and also reset something. It would work fine for a few cycles and then……same problem. I replaced the contactor in the inside unit and everything seams to be working now (2 days and all good). Ever since I replaced the contactor, the transformer has stopped humming. And yes, my unit has a transformer inside the inside unit. If it fails again, I’ll let you know.

        Reply
        • curious how it ran for days before noticing it wasn’t cooling. Without the fan running, it would ice up and stop cooling fairly fast. Glad you found the problem and are staying cool.

          Reply
          • Maybe I miss-spoke. It would cycle on-off for days just fine and then all of a sudden on one cycle the inside unit wouldn’t turn on and would freeze up quick……also, not sure it’s fixed now. The problem has recurred once since then. It may have something to do with the float switch. It “seamed” that the float switch (when tripped) is only preventing the inside unit from coming on but it’s letting the outside unit continue to run.

  153. Hello, I am just about at my wit’s end with this issue… I do not have 24 volts getting to the contactor, however when I manually press in the relay for the contactor, the unit appears to operate normally (fan and compressor kick on), but the air handler still only blows out hot air. Last summer the air handler motor had a broken mount and we replaced the motor ourselves, as well as the air handler. We took pictures of all of the wiring before disconnecting anything and are certain it is connected back properly, as it was working until this summer. I have also replaced the contactor, changing one wire at a time to ensure that each wire is connected exactly the same. Replacing the contactor may not have been necessary, but some of the contacts on it did look slightly pitted. I have noticed that the wires coming from the thermostat/air handler into the outside unit connect into a defrost board before connecting to the contactor, could there be an issue with the defrost board/circuitry?

    Reply
    • There is a float in the air handler, or the condensate pump that will prevent the outside unit from running if it doesn’t drain the water correctly. Is it possible that this got moved or damaged when replacing the fam motor? The 24 volts goes through a number of safety’s depending on the brand and the age of the unit. Follow the wires out until you find the device that has it shut down. Also, give it at least 5 minutes after the thermostat calls for cooling. When the thermostat is satisfied on temp, most units has a 5 minute timer to prevent short cycling of the compressor.

      Reply
  154. I was checking my unit out while my heater was on .Curiosity made me put my hand on ac compressor was getting cold .is this normal.Forgot to say my ac not blowing.That’s the weird thing heater works fine .I’ve concluded control board bad have nice little brown spot .Hoping I don’t have 1more issue and I hope I’m making sense.One more thing what brought this whole thinup I replaced my thermostat in Jan of this yr.2017 turned it on heat worked fine didn’t turn ac on until last wk. What the hell! ac worked summer before .

    Reply
  155. Help! My AC isn’t working. When I turned it on this morning, air started blowing out of the ducts inside right away. After about 30 minutes I realized that air was still blowing out of the ducts but my house was only 1 degree cooler (based on what the thermostat read) and you could feel that the house was not cooling off. I went outside to check the unit and it wasn’t on (but air was still blowing out the vents inside) while I was outside it kicked on (fan spinning and all) for about 15 seconds or so and then went off. I have since turned the whole unit off because I don’t want to burn anything up. Does anyone know what is going on with my unit!?

    Reply
    • Could be dirty condensing unit shutting down on high pressure due to lack of air flow. It could be that it’s low on refrigerant and shutting down on low pressure. There are other possibilities also, like a compressor failing and shutting down on high amps. It could also be a defective run capacitor on the compressor as well. You need to have a tech check it out as it probably calls for metering to diagnose.

      Reply
  156. I need some help on this one. My a.c. runs fine. The air is cold and the house seems to get cooler. However if the thermostat is set at 73 the a.c. will run and continue to run even when the thermostat says that is 72 inside. If I go and manually change it the temp aetting to say 74 the ac shuts off. It will then turn back on when the temp reaches above 74. The problem isnt the ac turning on it’s that it doesn’t automatically turn off

    Reply
    • sounds like a bad thermostat

      Reply
    • Digital thermostat or mercury? Could be out of level if it’s a mercury, or the heat anticipator set wrong. Is the thermostat in the sun? Is it on an outside wall? How old it the unit/thermostat. Many questions mostly pointing at the thermostat.

      Reply
  157. Help.. My AC won’t kick on. The breaker in electrical panel is tripped and won’t reset. Could it be bad fuses outdoor ib box near unit? Or a bad breaker?

    Reply
    • last time I had a breaker that wouldn’t reset it was the compressor that shorted out. I’m not an A/C guy but that’s my experience.

      Reply
      • Could be the fan motor, but you are more than likely correct. Regardless, it need an electrician to check it out, or a good refrigeration/AC tech High voltage can hurt, or kill. Be careful. And remember, capacitors can hold a charge for some time.

        Reply
  158. Ok so I have a trane xl16i outdoor unit that quit working the other day. So me being the diyer that I am decided to take a look and I found 2 fried snakes around the capacitor. I changed the capacitor yesterday and when I flip the breaker the unit will run for about 4 hours drop the temp a few degrees in the house then die. Any ideas or advice would be awesome thanks

    Reply
  159. Our AC blows air but it’s not cooling inside and the fan is not spinning and making some noise. What would be the cause/problem of it?

    Reply
  160. My a/c works, but we have to reset it each time for it to work. The heat works fine, but if we switch it from heat to a/c, the a/c won’t cool unless we turn off all the breakers, wait 20 minutes and then turn them all back on. Any ideas what the problem could be?

    Reply
  161. AC doesn’t come on inside but fan blowing outside. Right before this the smoke detectors alarmed and there was a burning smell in the house. No source could be found. Next we discovered AC not working.

    Reply
  162. exterior AC unit wont turn off. Last year, all was running fine. We recently turned on the ac for the first time this season. (yes we replaced filters & such) It was running fine as far as we knew. Then the weather got cooler so we turned off the AC at the thermostat that evening & went to bed (no heat/no AC on at all). When I went out back the next morning to the garden, I found the outdoor unit was still running & had ice on the pipes connecting to the unit, despite the thermostat being turned off. I shut off all breakers & let the unit thaw. My first thought was the thermostat went. So I replaced the thermostat but every time I wire it, the outside compressor clicks on & begins to run even thought the thermostat is set to off. The only way to shut it off is to un-wire the thermostat or turn off the breaker to the outside unit. Concerned it might be a short in the wire to the thermostat, I rewired the thermostat & I tested the heat. This seems to be working fine with no issues at all & clicks on with no problem & shuts down with no problem when it comes to temp. So, correct me if I’m wrong, but I figure if the heat is working fine that there is no short in the wire to the thermostat & that the issue must be with the outside unit in some way. ANY SUGGESTIONS???? Thanks in advance for any suggestions or advice that might be provided

    Reply
    • Try checking your contactor and make sure it is not stuck. Your thermostat will send a signal to your contactor to open or close depending on the temperature set point. This contactor when closed engages your compressor. Disengaged when open. Turn your condenser off at the breaker before checking. You will find directions online if you Google your make and model A/C

      Reply
  163. Ac blowing but not cooling, had someone come check it and they recommend it to replace the unit which is very pricey. What are my options to fix it and if I really need to replace it, how much should I be paying?

    Reply
    • Get another opinion from a reputable HVAC company. Some companies are simply salesmen, If he can’t tell you exactly why he recommends replacement, and what exactly is wrong with yours, then you can’t make an informed decision. How old is this unit?

      Reply
  164. We just got a new carrier, huge one, $7400 worth. We had it set on 76 and it stayed at 78 inthe house. So I fought to get the installer back, turns out there was a wire loose. Now we can tell it’s running, but rooms were still hitting 77-78° during the day. Turned it down to 74, the only room nicely cool is the living room, bedrooms at that end of house, mine stays at 77-78. What does That ambient degree or temp mean? My kitchen stays at 77°, 78-79 if cooking! I want to call another separate a/c company to get a review of the work done. Sounds reasonable? Thanks

    Reply
    • With a typical system, different rooms are going to have varied levels of cooling. Size of ductwork, distance from the A/C to the room, and the solar gain (south or west side vs. north or east side) are all going to make a difference. You probably need to have somebody come out and try to balance the system. The other option is to go with a zoned system (see https://www.hometips.com/buying-guides/zoned-heating-systems.html).

      Reply
      • Thank you, that sounds reasonable . I will call the installer back out here. It’s funny though, if we turn down to 73°. It goes to 76 at least throughout the house. Thanks again

        Reply
  165. My Carrier A/C runs but not steadily. It comes on then goes off a second later and it does this all the time now. It is about five years old. The unit sits on the roof. Please give me your best guess. Do I already need a new one? Thank you.

    Reply
    • That is an indication that it is low on refrigerant. But could be other things, like a plugged condenser not allowing cool air to flow and it’s over heating. Could be a dirty filter causing low pressure to cut out. You need a tech.

      Reply
  166. Have an older central air unit needs to be recharged every summer. Called a service guy to rechargce, said yes there’s a leak but the only way to see if it will hold freon is to give it a full charge that it won’t work properly if it doesn’t have proper amount of freon. Is this correct? The next day freon had leaked out $190 wasted. He said they don’t really fix leaks because there could be several and too expensive to fix. Is this correct? Thanks, joe. Chicago

    Reply
    • Absolutely not correct. They are not a service company if they don’t locate leaks. In fact, if they are charging this unit annually or more. There is a law that requires service companies to repair leaks if over a certain amount of Freon is expelled into the air. I don’t remember what that number is.
      But the point is, you need a reliable service company to find that leak and fix it.
      Also, the excess Freon is what cools the compressor motor. Every time it runs low on refrigerant, that motor is getting extremely overheated. Get another tech in there before you loose the compressor. These people are only Freon salesmen. That’s all they know how to do IMO.

      Reply
      • I agree with you this is the first time I used this company. The unit is about 29years old and he was assuming there would be more than one leak and between repairing and more Freon that was already wasted the cost would outweigh fixing the old unit. Said a replacement would run about 2,750. I have tenants renting so for this year I had to go out and buy some window units to get them through this summer, Hopefully will be in a better situation next year to fix it/replace it, Thanks for your response.

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  167. My AC unit stopped cooling my home. The fan is running outside and I do hear an occasional “hum” coming from the unit. I was told that the compressor was bad and that I needed to replace the whole unit. What’s weird is that it was working just fine the day before. I am disabled and on a very fixed income and unable to afford a new unit. I have difficulty breathing when it is hot and humid and desperately need my AC fixed. Is there any advice you can offer??

    Reply
    • A service tech needs to check the capacitor for the compressor. You didn’t say if any one tested it and confirmed that the compressor is bad. If it was diagnosed over the phone, then call a dependable company that is not just out to sell you a new unit. If it was looked at, did the tech take a meter and check the compressor?
      Tell them what you told us. You can’t afford a new unit so you need this one fixed if it’s a reasonable price.

      Reply
      • Pat, thanks so much for all the help you have given to the discussions in this forum!!

        Reply
  168. I live in an apartment and my AC does not cool my apartment at all during the day. If it is 90 outside my AC temp gets up to about 86 and keeps running. I have my AC set on 78. Shouldn’t the AC keep your apartment at the temp you set it at? I know that each room is going to be different temp’s. The people at my apartment complex say’s the AC is not going to cool my apartment to that temp and keep it there.

    Reply
  169. Last year my central air stopped working and I found the capacitor “exploded” apart. The top was off when I looked into. I replaced it with a capacitor from grainger. I made sure all the numbers matched. The only difference was the maker of the capacitor and it was a lot bigger in size than the old one. It worked “ok”, but it was not cooling like it used too. It was towards the end of the hot season so I waited until this spring to have it tuned up and checked by a pro. It worked fine at that time. 10 days ago it stopped getting to the set temperature again. I noticed the copper line outside freezing over. I had a pro here 5 days ago and he couldn’t get it. The next day a “master” pro came and thought he found the problem. Well, the lines aren’t freezing anymore, but it is still not cooling. I am going to call them back because they have a 90 day guarantee, but I am looking for anything I or they might be overlooking. It seems like an air flow issue, so I will be vacuuming out the ducts today. Thanks for any help.

    Reply
  170. Hi, I’ve searched everywhere for an answer to what’s going on with my A/C, so hoping someone can help. The heat worked fine all winter, then when we got the first warm day here in Michigan, I set it to cool, and tried to set the thermostat, but I didn’t hear the “click”, and it never came on. I decided to take the cover off of the thermostat to check the wires, and as soon as I took the cover off, it came on. It seems to be cooling okay, though we have not had really hot days. It will not shut off, unless I put the cover back on… I am clueless as to what is going on, and really don’t want to call a service person, until I do have at least some idea of what could be going on. I bought a new thermostat, (replacing it with a digital thermostat), thinking that was the problem, but when I tried setting it up with the same wiring as the old one, it just runs constantly, with no way to shut it off, so I put the old one back on, just so we can have some air until I can afford a service call. Any thoughts? Thanks!

    Reply
    • Hi Debbie,
      Wow, this sounds frustrating. You tried what I would try first—replacing the thermostat. But you say you set it up with the same wiring as the old one. Be sure to read the instructions for wiring the new one rather than just replacing the wires per their colors, etc. The new thermostat might have a slightly different wiring configuration. Sounds to me like it’s mis-wired. Please let us know what you learn.
      Please see the discussion below from 2 months ago between Kris Snopek and Steven B.—looks like the same issue. Steven say’s a “stuck contactor” may be the issue.

      Reply
  171. I’ve got a 18 year old 3-ton Rheem outside central air unit. The repairman came out and recharged the unit which was totally out of Refrigerant. He said it had a leak on the low pressure side. Whatever that means…Then after charging me $198 he said the necessary repair to the unit would be $3175. or $4346 for a new Seer. SInce I can’t afford either, being on a fixed low income and retired with no credit rating, is there a reasonable way to get this fixed?

    Reply
    • Some types of leaks can be repaired…but that seems like a lot of $$ for repair. If he tested for the leak and found it (rather than just checking the pressure), ask him specifically where it is. Then get bids (and opinions) from a couple of more AC contractors. Be aware that they would rather sell you a new unit than repair the old one because a commission might be involved.

      Also, see the discussion between Joe and Pat McBride a month ago (below). It involves a similar situation.

      Reply
  172. Help! Our ac is running but not keeping house cool. Had ac guy come out, unit freezing up. Turned off unit and acid flushed lines, worked one day. Tech came out again and changed motor and fan. Unit started to cool off house after about six hours. It was at 72° at about 8 am, it is now 79° in house at 1 pm. What else could it be? Evaporator coils, capacitor? We can’t afford a new unit but also can’t live with it being 90° in house. Thanks everyone!!

    Reply
    • As far as I know, two things cause an AC air handler to freeze up. By far the most common is reduced air flow because of dirty filters, coils, or poorly working fans (which, it seems, is what your tech figured). The other is low refrigerant level, which a pro must check and, if necessary, recharge. If I had paid for a day’s work and a new motor and fan, I would want the tech to tell me why he did these things and yet I still don’t have satisfaction. Then I would expect him to come out and give me a great deal on getting it right.

      Reply
  173. Can a leak on the low pressure side be repaired reasonably?

    Reply
    • John, hopefully an AC contractor who visits our site will answer this. Please see my answer to your first question, below.

      Reply
  174. Hi there. I have a condo-sized central A/C situated in the hallway ceiling. It’s about 10yrs old. My thermostat is there also. After being out of town for a few weeks, I returned to see that batteries in the thermostat had run down and were flashing. No problem I thought. I inserted fresh batteries, made sure that the cool and fan settings were set and all I heard was a click from the ceiling unit overhead – as if it was trying to engage. Nothing else. Does this sound like an obvious fix? Did the fact that the batteries in thermostat which I kept at 78 powered-out for an unspecified period of time affect the unit? Does this sound like a complicated repair? Thanks again, any help is greatly appreciated.

    Reply
    • ZZyzx, you have a very unusual name…always the last on the list, I’ll bet :) I don’t think the batteries would cause this. If your outdoor unit won’t come on and and you hear a clicking noise followed by a soft hum or buzz your AC capacitor probably needs replacement. If you hear a click but no hum or buzz, the contactor—a relay to the compressor—probably needs replacement.

      Reply
  175. Hello, have an issue with ac not cooling down home. Thermostat set at 77 and temp rises during the day to 81/ 82 degrees and never gets down to 77. until later at night. Lower the thermostat and still result during the day is the same although at night never gets lower than 77. Had sears tech today. Said system overcharged and adjusted to correct amount. On going issue. 3 ton carrier, 2003 install, 1550sq ft manu fact home and ceiling vents. Any Ideas, thanks

    Reply
    • I am trying to find out if my ac is right size. It is 2.5 ton New Lennox installed in 2016. My house is 1,096 square feet. The air coming out of the compressor fan is cool and the unit does not cool my house below 84° even though the thermostat is set at 70°. I hope some of you might know what is wrong. Any ideas Greatly Appreciated.

      Reply
      • Generally speaking, you can multiply your square footage by 25 to get the proper BTUs needed for cooling. So 1096×25=27,400. Figure roughly 12,000 BTUs per ton. The math: 27,400/12,000= 2.28. So a 2.5-ton unit is about right. Looks to me like F. Sager’s is properly sized.

        Carol, your math is 1550×25=38750. Then, 38750/12000=3.29 so your 3 ton Carrier looks very slightly undersized, but should handle the jobs except in very high heat/humidity conditions. On those days, block heat gain with curtains, etc., keep the air moving with fans, and minimize using heat- and moisture-producing appliances during the day. Ultimately, you might need better insulation, etc.

        Reply
  176. Help I’m hot my ac is making a noise

    Reply
    • Helene,
      We’d like to help but can’t do much unless you give us a lot more detail.

      Reply
  177. Hi Don, we have a central air with a rooftop thermometer sadly during winter it is cooling and heats in summer (at least at the begging of the season) today the reading was 18 degrees (roof reading) and selecting 24 degrees inside still blew cold air! What could be the issue?

    Reply
    • Val, I’m not familiar with a rooftop thermometer…is this on a house or an RV? I can’t understand why an AC unit would be controlled by a thermometer that measures outdoor temperature. Please explain what is going on here.

      Reply
  178. The outside part of the ac is running, but I cannot hear the inside blower? Part running. When it gets hot in my house and the ac is not on, and the temp gets to 90degrees I hear a blower or fan running, sounds like the ac when it is on, now that happened today and so I turned on the ac and the blower/fan turned off. Do I need to replace the thermostat again or what should I check

    Reply
    • Please clarify. When you turn on the AC is the outdoor compressor running? Is the blower in the indoor air handler (or furnace) running and blowing air through the registers? Is the air cold? Does anything you do make the blower come on?

      Reply

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