Causes of Air Conditioners Freezing Up

Outside Temperature

• Outside temperatures below the thermostat limit will cause the coils to freeze, if the unit is running. An air conditioner unit's normal thermostat low is between 60 and 65 degrees. When you turn the unit to its lowest setting, the warmer air inside the unit mixes with the colder outside air, which produces condensation and freezes the cooling components of the air conditioner. You can expedite the thawing process by turning the fan on high and raising the thermostat to its highest setting, which is around 86 degrees Fahrenheit for some units.

Broken Fan

• If you can hear the air conditioner compressor operating and the internal fan blowing, then you can turn the air conditioner off to melt the coils. If the fan doesn't run, however, and the compressor is still working, this might be the cause of the internal components freezing. Turn the mode to "Fan" or press the "Fan Speed" button to get the fan to turn off. If the fan fails to turn on, then the fan might be broken. If the fan is broken, the air conditioner won't work. Contact an air conditioning technician to fix the fan.

Debris

• If the fan isn't blowing but the internal compressor works, the fan might be blocked by debris or garbage, such as a plastic bag that possibly got sucked into the unit. Open the front grille of the unit and inspect the inside for blockage. If possible, unscrew the cover and inspect the inside of the unit for any signs of debris. Put the cover back onto the unit and turn it on.

Thermostat

• You should test the thermostat before taking the air conditioner apart to determine if it's working correctly. If the thermostat fails to shut off the compressor, then the thermostat is broken and the compressor can't be shut off unless the power is turned off. Try raising the thermostat setting. If the room temperature is lower than the set thermostat, then the air conditioner compressor should shut off.