Air Conditioner is short cycling

If your air conditioner is short cycling, meaning the AC turns on and off quickly instead of completing a normal cooling cycle, the problem is usually tied to the controls that tell the fan and compressor when to run. Start with the control board, then the main control board, since either board can send incorrect voltage to the air conditioner components and make the air conditioner keep cycling. The user control and display board is another likely cause, especially if the settings respond poorly or the unit behaves inconsistently. If those boards check out, test the thermistor or temperature sensor, which read room air temperature and report back to the control board. A bad sensor can make a window AC short cycling problem look like a major compressor issue. The temperature control thermostat can also cause short cycling if it shuts the compressor off too soon or does not allow enough restart delay. Enter your model number on RepairClinic.com to find the exact replacement control board, thermistor, temperature sensor, thermostat, or display board for your specific air conditioner.

01 - Air Conditioner Control Board

The control board regulates the voltage to all of the air conditioner components. If the control board fails, the air conditioner may short cycle. Control boards are often misdiagnosed; make sure to check more commonly defective parts first before replacing the control board.

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02 - Air Conditioner Main Control Board

The main control board regulates the voltage to all of the air conditioner components. If the control board fails, the air conditioner may short cycle. Control boards are often misdiagnosed; make sure to check more commonly defective parts first before replacing the main control board.

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03 - Air Conditioner User Control and Display Board

The user control and display board allows the user to operate the unit by selecting fan speeds and cooling temperatures. If the board is defective, the air conditioner may short cycle. If the temperature sensor or thermistor tests appropriately with a multimeter, it's possible the user control and display board is malfunctioning and will need to be replaced.

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04 - Air Conditioner Thermistor

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 check...ing your user’s manual.)

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05 - Air Conditioner Temperature Sensor

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 us...er’s manual.)

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06 - Air Conditioner Temperature Control Thermostat

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 contr...ol 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.)

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07 - Air Conditioner BTU Rating is Too High For The Room

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.

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