How to Fix AC That's Not Turning On – Air Conditioner Repair
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How to Fix an Air Conditioner That Will Not Turn On

About this repair:

  • Rated as REALLY EASY
  • 25 repair stories

Electronic Control Board or PCB Assembly

If your air conditioner will not turn on and you have confirmed that the power source is good, the problem may be the electronic control board, also known as a PCB assembly. This part is commonly used in window air conditioner units to help control the various parts. A sign that the control board is not working is the fan or compressor circuits not turning on. Check the control board for a blown fuse, first consulting your user manual to ensure your control board has an internal fuse. Replace your control board with a board with the same specifications.

Thermostat or Temperature Control

If your air conditioner does not turn on, there may be an issue with the thermostat or temperature control. This is especially common in models which have a rotary type thermostat or control, which utilizes a sensing bulb to monitor the air temperature in your room. If the air needs cooling, the sensing bulb will signal the compressor. First check that the power source to your air conditioner unit is good, then try to turn the temperature control, which should trigger a light click noise. If everything appears normal, you can test the thermostat contacts for continuity using a multi-meter.

Power Cord

Your air conditioner may not turn on because of a faulty power cord interrupting the power supply. Test the outlet you are using with a different appliance to make sure it is supplying power. Visually inspect the power cord for signs of damage such as fraying. If your window air conditioner is on the newer side, it should feature a circuit breaker in the power cord; check to see if the breaker has tripped. If everything appears normal, remove the cabinet and use a multi-meter to test the terminal strip for voltage. Do not attempt to repair the power cord, replace it if it is faulty.

Thermistor or Temperature Sensor

If your window air conditioner won’t turn on, there may be a problem with the thermistor or temperature sensor. This component, particularly common in newer models, helps control the function of other air conditioner parts. The thermistor acts as a sensor to help monitor the air temperature in the room and signals the control board to turn the compressor on and begin circulating cool air. To test the thermistor, check your user manual to find out the proper specifications, and then use a multi-meter to confirm if it is working. If the thermistor appears to be working, inspect the control board for damage or a loose connection.


Your window air conditioner may not turn on because of a blown fuse. The fuse, particularly common in newer models, helps protect the electronic control. Check to ensure that the power supply to your unit is good, then unplug the air conditioner and remove the cabinet cover. The fuse will be located near the circuit board; check to see if it has blown, using a multi-meter if necessary. Replace the fuse if it has blown.

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