Why Do Slots of an Air Conditioner Freeze When Ice Forms?

Fan Bearings

• If the fan turns but struggles in doing so, the fan bearings might be to blame. To determine what’s wrong with the fan components, remove the front panel of the air conditioner to access the fan compartment. All power to the unit should be turned off or unplugged to avoid shock and disable the fan completely. A spin of the fan by hand should give you the first sign of the state of the fan bearings. If the fan turns freely, the bearings are fine. If the fan turns with resistance, then the bearings need to be lubricated. Applying electric motor oil to the lube ports of the fan motor, followed by a few spins of the fan, should do the trick.

Evaporator Coils

• A dirty cooling element could be the cause of icing on your air conditioner. The unit should be cleaned approximately every year to avoid ice buildup. You can shine a flashlight into the unit, after removing the front panel, to get a look at the coils. If they are dirty, the coils can be removed and washed with a solvent-based cleaner. Before you remove the cooling element, unplug the air conditioner to avoid electrocution. After the coils are thoroughly cleaned and dried, the element can be placed back into the unit.

Thermostat

• If the thermostat is disconnected from the cooling element or is damaged, the cooling element may stay activated long after the fan has shut off, causing the unit to freeze. The fan must blow the cold air away from the cooling element, or the unit will freeze every time. The first way to test the thermostat is to raise its setting above room temperature and listen for the internal compressor to shut off. If the internal compressor doesn’t shut off, then the circuit between the thermostat and the cooling element is either open or faulty. If you remove the front panel and discover that the thermostat wiring is disconnected from the rest of the unit, reconnect it. If the unit still fails, contact a technician.

Outside Air

• Colder air outside will cause the unit to freeze if the unit is in active cooling mode. The cool air outside clashes with the warmer air inside and creates condensation, which then freezes inside of the unit even though the fan still operates. You can turn the unit off to allow it to thaw then restart it with the thermostat raised and the fan set to low.