How to Fix an Air Conditioner That Is Constantly Running

If your air conditioner will not shut off and keeps blowing cold air, it may be due to an issue with the control board, also known as the PCB assembly. A sensor monitors the air temperature in the room and signals the control board to turn on the compressor and begin cooling. The board relays may be faulty if the compressor keeps running well after the ideal temperature has been reached. The board processor circuitry may also be the source of the issue. Some air conditioner units have a separate relay board, in which case you can use a multi-meter to test each relay output for continuity and determine if one is at fault.

You air conditioner may not shut off or stop blowing air because of an issue with the temperature control, also known as a thermostat. For rotary dial thermostats, there will be a set of internal electrical contracts which power the compressor circuit, to signal it to blow cold air. This set-up utilizes a sensor bulb, located near the evaporator coils, to monitor room air temperature. If the temperature control contacts become stuck in the closed position, the compressor will keep running after the ideal temperature has been reached, and keeps blowing cold air. Check the sensor bulb to make sure it is properly attached to the coils before replacing the temperature control.

If your window air conditioner will not shut off, it may be due to a problem with the thermistor or temperature sensor. The thermistor is located near the evaporator and monitors the air temperature in the room. It signals the control board to turn the compressor on or off as required. The temperature sensor or thermistor may not be working if the air conditioner is not shutting off, because it isn’t getting the message that ideal temperature has been reached. To test the sensor, check your manual to find the exact specifications for the thermistor and measure with a multi-meter. Check the other components such as the control board for any visual signs of a loose connection.