Window Air Conditioner

ambient thermistor

DID YOU KNOW: Once you turn AN air conditioner off, YOUR SUPPOSED TO leave it off for several minutes before restarting it?

AIR CONDITIONER'S Compressor humming but not working?


If you turn the air conditioner off and then back on too quickly, the pressure of the refrigerant gas rises too high; as a result, the compressor hums and won't start until the refrigerant pressure equalizes between the evaporator and condenser coils.

Other reasons the compressor is humming but not starting include a dirty or otherwise restricted condenser coil.

If your window air conditioner isn’t cooling properly, it may need a new ambient thermistor. You can replace the ambient thermistor yourself very easily following these instructions below.

Repair difficulty


Time required

45 minutes or less

Control buttons or lights on the user interface control board can stop working. This repair guide shows how to replace it.

Replace the window air conditioner compressor

The compressor is a pump that compresses the refrigerant-Freon-that's sealed in the window air conditioner. If the compressor doesn't run when activated, have a refrigerator service technician replace it; by law, an EPA-licensed technician must do this repair because it involves Freon.

Main causes: bad compressor, lack of refrigerant, bad compressor start relay, electronic control board failure

Main causes: clogged condensate drain, air conditioner not leveled properly, leaky window air seals

Main causes: lack of electrical power, bad electronic control board, wiring failure, bad temperature sensor

Main causes: clogged drain hole, air conditioner not leveled properly

Main causes: dirty air filter, air conditioner is too small for the room, temperature set too cold, control failure

Main causes: turning the air conditioner off and the back on too quickly, dirty or restricted condenser coil, compressor failure