Why Do Air Conditioner Lines Ice Up?

Reversed Fan

• Some air conditioner units feature a fan motor with a directional switch. The directional switch allows you to choose which direction the fan blows. If the fan is set to reverse, meaning it doesn't blow the cold air out of the unit, then the cold air generated by the cooling element creates ice inside of the unit. Panels of the air conditioner can be removed with a screwdriver to reveal the fan compartment. If the fan contains a switch, flip the switch to reverse the fan to the correct direction. If no switch exists and the fan blows in the wrong direction, you can uninstall the fan, turn it around and reinstall it onto the fan motor.

Debris

• It's possible for unwanted materials to get sucked up into the air conditioner unit through the intake grille. These objects, such as string or a plastic bag, could potentially wrap around the fan component and prevent it from blowing. Before removing panels to access the fan compartment, the power should be shut off from the unit to prevent the fan from burning up and to prevent shock. After the debris is removed from around the fan, conduct a test to ensure that the fan still works. If the fan is damaged, a technician should be called to repair the unit.

Cold Outside Air

• Cold or freezing temperatures outside work against your unit, if the unit's cooling element is enabled to cool the room. The colder air from outside mixes with the warmer air inside and causes the cooling element to freeze up. Leave the unit turned off to allow it to thaw, then you can run the fan only, open the vent or run the unit on low at a high temperature.

Thermostat Connection

• If the thermostat is unable to communicate with the fan, then the fan fails to run in tandem with the cooling element, causing the unit to freeze. One way to test the thermostat is to turn it down below room temperature and listen for the fan. If the internal compressor activates without the fan, then the thermostat is either broken or the circuit between the fan and thermostat is open. If you have a central air conditioning system, call a technician for help. If you have a window unit, you can remove the front panel and examine the wiring between the thermostat and the fan motor.