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Air Conditioner Won't Turn Off

The part(s) or condition(s) listed below for the symptom Air conditioner won't turn off are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.

Most Frequent Causes for Air conditioner won't turn off

For the most accurate results, enter your model number.


Cause 1Condenser Coils are Dirty

The condenser coils dissipate the heat as the refrigerant passes through the coils. If the condenser coils are dirty, they won’t be able to dissipate the heat as effectively. As debris builds up on the coils, the air conditioner will become less efficient, causing the air conditioner to work harder to cool down. If the coils are significantly dirty, the air conditioner will not be able to maintain the proper temperature, and the compressor will run continuously in an attempt to cool the room. Check the condenser coils to determine if they are dirty. If the condenser coils are dirty, clean them.

Cause 2Temperature Control Thermostat

The temperature control thermostat provides voltage to the fan motor and compressor. If the thermostat has shorted out, it might send continuous voltage to the compressor and cause the compressor to run all the time. To determine if the thermostat is shorted out, use a multimeter to test it for continuity. If the thermostat has continuity all the time, this indicates that it is shorted out and should be replaced. (Note: Some thermostats may also control a heater and, as a result, will have three terminals. Refer to your air conditioner’s wiring diagram for more information.)

Parts
Cause 3Thermostat

The thermostat monitors the temperature of the air. When the air temperature rises above a set point, the thermostat activates a switch to provide power to the fan and compressor. If the thermostat is defective, it may cause the compressor to run continuously. To determine if the thermostat is defective, set the air conditioner to cooling and then use a multimeter to test the thermostat for continuity. If the thermostat does not have continuity while the air conditioner is set to cooling, replace the thermostat. (Note: Some thermostats may also control a heater and, as a result, will have three terminals. Refer to your air conditioner’s wiring diagram for more information.)

Parts
Cause 4Thermistor

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. If this happens the compressor runs all the time.

Parts
Cause 5Relay Board

The relay board provides voltage to many of the air conditioner components, including the fan motor and compressor. If there is a problem with the relay board, it might provide continuous voltage to the compressor. However, this is almost never the case. Before you replace the relay board, make sure you check more commonly defective parts. If you are certain that all of the other components are working properly, replace the relay board.

Parts
Cause 6Temperature Control Board

The temperature control board provides voltage to the fan motor and compressor. If there is a problem with the control board, it might not stop providing power to the compressor. However, this is almost never the case. Before you replace the temperature control board, make sure you check more commonly defective parts. If you are certain that all of the other components are working properly, replace the temperature control board.

Parts
Cause 7Main Control Board

The main control board provides voltage to all of the components of the air conditioner. If there is a problem with the control board, it might not stop providing power to the compressor. Before you replace the main control board, make sure you check more commonly defective parts. If you are certain that all of the other components are working properly, replace the main control board.

Parts