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Air Conditioner Will Not Cool

If your central air conditioner will not cool but you can hear it running, it may just need to be cleaned. Whether or not this is the cause of the problem, it’s the first remedy to try. Plan to do this on a relatively warm day. The following are guidelines; always refer to your owner’s manual.

air conditioner will not cool

Turn off the circuit breaker that serves the AC compressor.

1Turn off the power to the AC unit. There is normally a shut-off or disconnect panel on the wall next to the outdoor compressor. Also shut off the air conditioner’s 240-volt circuit at the main electrical panel.

2Rake leaves and debris away from the outdoor condenser. Trim any bushes that might block airflow.

3Unscrew and remove protective grilles and the top cover or grille from the compressor. If the fan is attached to the grille, be careful not to pull any wires loose.

4Use a soft brush to clean dirt and debris from the fins, and then vacuum the fins with a brush attachment (taking care not to damage them).

5Use a hose and nozzle with a trigger grip to spray debris from the fins (from inside the unit). Protect the wiring and motor from water with plastic sheeting or a large plastic garbage bag. If your owner’s manual calls for lubricating the motor, do that now—but don’t over-lubricate.

6Reassemble the unit.


7To test it, turn the thermostat to OFF, reset the power at the disconnect next to the compressor and the main panel, and then set the thermostat to ON. To avoid straining an air conditioner’s compressor, wait at least five minutes between turning it off at the thermostat and turning it back on. Let it run for a few minutes, and then feel the two pipes that connect the condenser unit to the air handler (slide any insulation back). One should feel warm, the other cool.

air conditioner will not cool

Air conditioner technician checks refrigerant levels.

If the air conditioner still will not cool, call an air conditioning technician—the refrigerant may need recharging.

get air conditioning hvac pro

For more on maintenance tips, see Preparing Your Air Conditioner for Summer.

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

About Don Vandervort
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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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  1. what damage get be done to an ac unit, if it accidentally gets turned on in the winter while covered with tarp and snow/ frigid weather

    • This typically causes the compressor unit to overheat. Hopefully the overload triggered and shut it down. If so, it should be okay. When the weather gets better, uncover it and try the AC to see if all is well.

  2. I have a brand new inside and outside unit, both full of freon, and it still blows barely cool. My A/C will stay on all day long. I’ll set it to 74 and leave for a few hours, come back and it’s 80 in the house. Any ideas?

    • I have the same problem & cant figure out why either.

      • Same issue here but no solution

        • It got the same problem also..I had one company come out and say it was a little low on freon. He came back again and said it was still a little low. After that didn’t do anything for me I had another company come and say everything looked good and didn’t know why it wouldn’t cool. I’ve done all the DIY tricks before calling. I have a 2.5 yr old house with great blow in insulation. Last year I never had a bill over 120 in the summer months. I just got a bill yesterday for 300. I’m so frustrated on what I need to do. I’ve been going at it for a month now.

  3. the electric company came out this morning and cut off electricity for a couple hours when it came back on my a/c unit isn’t blowing cold air anymore. Any ideas of what i should do?

    • Turn off the A/C at the thermostat. Next, at the electrical box that serves the A/C, reset the circuit breaker for the A/C by flipping it to Off and then back to On. Wait 30 minutes. Turn the thermostat back to Cool and set the temperature lower than the room temp so it will turn the system on.

  4. there are no fuses in the power box going to the unit but some of the wires are exposed an now wet since its been drizzling, they are not like regular wires but arent all wires suppose to be covered by eletric tape or duct tape?

    • Wires should not be exposed unless they are bare ground wires. Black electrician’s tape is sometimes used at connections (not duct tape). It sounds to me like a qualified electrician should take a look at this so nobody is in danger of serious shock.

  5. Our ac was working fine then it suddenly / stopped cooling. The fan runs but it is 82 in the house even though the thermostat is set to 72. Have turned off the breaker and then turned it back on….have checked the outside switch also. The fan spins but it just buzzes when the air tries to kick on. Any ideas?

  6. My unit is fairly new and the air conditioning over the last two summers was perfect. This year it is blowing out heat on the cool setting. I set it on 75 and my home was heated to 80 degrees today. Any advice?


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