If your heating equipment isn’t working properly, maybe the thermostat is defective.
Here’s how to see if it’s any good:
11) With the power to the furnace off, remove the thermostat or thermostat cover to expose the wires.
2Unscrew and remove the two wires from their terminals. Do not let them fall back in through the hole in the wall (wrap them around a pencil if necessary). If there are more than two wires, pick Red and White—normally these are standard colors for power and heat. For a problem with cooling, you would choose Red and Green.
3Wrap the two wires together.
4Turn the power on and watch the furnace. If the blower goes on and the furnace burner ignites, the thermostat is defective. Replace it as discussed in the article How to Install an Electronic Thermostat.
5If the burner does not ignite, check the continuity of the wires from the thermostat to the furnace. (If you’re checking the air conditioning, only the blower will go on.)
6Check and tighten the terminal screws at all wire connections.