How To Repair Air Conditioner That Won't Stop Running
- Rated as REALLY EASY
- 4 repair stories
- 3 step by step videos
Electronic Control Board or PCB Assembly
If your air conditioner is continually blowing cold air and doesn’t shut off even though the set temperature has been reached, you may have a problem with the control board. Modern window air conditioners often use an Electronic Control Board, sometimes referred to as the PCB, to control the functions of the individual components of the unit. A sensor device called a thermistor is used to monitor the room air temperature and this information is sent to the control board. Output relays on the board will control the fan and compressor circuits, turning them on and off to maintain the set temperature. If the compressor or the circulating fan and compressor remain on even after the temperature has been reached, you may have a defective relay on the board or the processor circuitry on the board may be at fault. In either case you will have to replace the complete control board. Some models may use a separate relay board and additional troubleshooting with a multi-meter would be necessary to determine which is at fault. Inspect the sensor for a poor connection or any signs of damage before condemning the control board.
Temperature Control
If your air conditioner doesn’t shut off even though the set temperature has been reached, and continues to blow cold air, you may have a problem with the thermostat. The rotary dial thermostat or temperature control has a set of internal electrical contacts that supply power to the compressor circuit, and also uses a capillary tube and bulb sensor that attaches to the front of the evaporator coil to monitor room air temperature. As the temperature on the sensor drops, a pressure change occurs at the control and the switch contacts will open and shut off the compressor. If the contacts weld or stick closed, the compressor will continue to run regardless of the temperature sensed by the bulb at the evaporator. Inspect the sensor bulb for any signs of damage before condemning the temperature control.
Thermistor or Temperature Sensor
Modern window air conditioners often use an Electronic Control Board, sometimes referred to as the PCB, to control the functions of the individual components of the unit. A sensor device called a thermistor is mounted near the front of the evaporator and is used to monitor the room air temperature. This information is sent to the control board where it is processed and used to cycle the compressor on and off to maintain the set temperature. If your air conditioner won’t shut off, you may have a defective temperature sensor. Testing of the sensor will require the technical specifications of the thermistor for your model and a multi-meter. Inspect the control board for any signs of a loose connection to the sensor as well.
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