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Air Conditioner Compressor Won't Run

The 10 most common part(s) or condition(s) which contribute to the symptom Air conditioner compressor won't run are listed below. Check or test each item and watch any available videos. If you are still unable to solve the problem you may need to do additional research and troubleshooting. Remember, with our 365 Days. Period.® return policy you can return any part for any reason. So, go ahead and buy it to try it. No other parts retailer offers this unconditional return policy.


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For the symptom you selected, these are the most common parts or causes, ordered by the likelihood of fixing the symptom.

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Temperature Control Thermostat

If the air conditioner compressor does not run, the temperature control thermostat might be defective. The temperature control thermostat has electrical contacts inside that burn out over time. It is possible for the thermostat to still turn on the fan motor but not the compressor motor.

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Temperature Control Board

If the air conditioner compressor does not run the temperature control board might be defective. The temperature control board provides the voltage to the fan motor and compressor. These boards are often misdiagnosed. Check all other components to be certain this is the cause of the problem.

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Thermostat

If the air conditioner compressor does not run the thermostat might be defective. The thermostat is a sensor which detects the room air temperature and a switch to provide power to the fan and compressor. If the thermostat is defective the air conditioner compressor does not run.

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Overload

Every air conditioner compressor has a small device called an overload. The overload protects the compressor from burning out if it draws too much current. Over time the overload itself can burn out. The overload can be tested for continuity to determine if a continuous electrical path is present.

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Compressor

If the air conditioner does not cool, the compressor might be defective. The compressor is a motor which compresses the refrigerant and circulates the refrigerant through the evaporator and condenser coils. There are several other components which are more likely to be defective if the compressor doesn't work. If the compressor itself is defective a licensed professional will need to replace it.

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Thermistor

If the air conditioner compressor does not run the thermistor might be defective. The thermistor is a sensor which detects the room air temperature. It is connected to the control board. If the thermistor is defective it will not have continuity when it should and can prevent the compressor from running.

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Relay Board

The relay board provides voltage to many of the components of the air conditioner. If the compressor does not run, there might be a problem with the relay board. Before replacing the board, check all of the other components - in particular the compressor's capacitor, overload protector and the compressor itself. The relay board is often misdiagnosed.

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Main Control Board

The main control board provides voltage to all of the components of the air conditioner. If the compressor does not run, there might be a problem with the main control board. Before replacing the board, check all of the other components - in particular the compressor's capacitor, overload protector and the compressor itself. The main control board is often misdiagnosed.

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Capacitor

Every air conditioner has a compressor motor. Every compressor has a capacitor attached to the electrical leads. If the capacitor burns out the compressor will not run. The capacitor can be checked with a special meter to see if it is defective.

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Selector Switch

Power flows through the selector switch to the compressor. If the compressor does not run the selector switch contacts might have burned out. If the compressor will run intermittently by pressing the selector switch buttons or rotating the switch knob, replace the switch.

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