Window Air Conditioner: 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. Once you turn the air conditioner off, leave it off for several minutes before restarting it. Other reasons the compressor is humming but not starting include a dirty or otherwise restricted condenser coil or the short cycling of the compressor.

window air conditioner

These repairs may help solve your window air conditioner problem

Replace the window air conditioner compressor

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.

Symptoms for window air conditioners

Choose a symptom to see related window air conditioner repairs.

Main causes: bad compressor, lack of refrigerant, bad compressor start relay, electronic control board failure
Main causes: turning the air conditioner off and the back on too quickly, dirty or restricted condenser coil, compressor failure
Main causes: dirty air filter, air conditioner is too small for the room, temperature set too cold, control failure
Main causes: clogged drain hole, air conditioner not leveled properly
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

Repair guides for window air conditioners

These step-by-step repair guides will help you safely fix what’s broken on your window air conditioner.

How to replace a window air conditioner ambient thermistor

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

Repair difficulty
Time required
 45 minutes or less
How to replace a window air conditioner user interface control board

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

Repair difficulty
Time required
 30 minutes or less
How to replace a window air conditioner electronic control board

The electronic control board is the brain of your window air conditioner. Here’s how to replace it.

Repair difficulty
Time required
 45 minutes or less

Articles and videos common to all room air conditioners

Use the advice and tips in these articles and videos to get the most out of your window air conditioner.

September 26, 2019

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