Air Conditioner is Short Cycling

The thermistor is a sensor connected to the control board that detects the temperature of the air. The resistance value of the thermistor changes in conjunction with the air temperature. If the air temperature rises, the resistance value will decrease. A malfunctioning thermistor may cause the air conditioner to short cycle. To determine if the thermistor is at fault, use a multimeter to test it for continuity. If the thermistor does not have continuity, or if the resistance of the thermistor does not change with a change in temperature, replace the thermistor. (To find specific temperature and resistance values, try checking your user’s manual.)

The temperature sensor is connected to the control board and detects the temperature of the air. The resistance value of the sensor changes in conjunction with the air temperature. If the air temperature rises, the resistance value will decrease. A malfunctioning temperature sensor may cause the air conditioner to short cycle. To determine if the sensor is at fault, use a multimeter to test it for continuity. If the sensor does not have continuity, or if the resistance of the sensor does not change with a change in temperature, replace the component. (To find specific temperature and resistance values, try checking your user’s manual.)

The temperature control thermostat is a sensor which monitors the temperature of the air and activates a switch to provide power to the fan and compressor when the air temperature drops below a set point. If the thermostat isn’t working, the air conditioner may short cycle. When the thermostat shuts the compressor off there needs to be approximately a five to ten minute delay to let the refrigerant equalize before the compressor will start again. If the refrigerant has not had time to equalize the compressor may not start. If the thermostat is short cycling it will need to be replaced. To determine if the temperature control thermostat is defective, use a multimeter to test it for continuity. If the thermostat does not have continuity, replace it. (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.)

An air conditioner will do two things: lower the temperature and lower the humidity. In order to remove the humidity from the room the air conditioner needs to run longer between cycles. If the unit is shutting off after 15 minutes of run time on a hot day, the unit's BTU (British Thermal Unit) rating is likely too high for the size of the room. To keep the unit running longer you can try setting the fan to a lower speed. The longer the unit runs between cycles the more humidity will be removed from the room.