Air Filters
Air conditioning units can freeze up for a variety of reasons, and there are a few things that can be checked by the homeowner before a repairman has to be called. If the unit is frozen, turn it off and turn the fan to the "on" position instead of "auto." This will create airflow that will help thaw the coil. Check the air filters. There will be one near the unit itself and also in the air returns in the house. They need to be clean in order for the system to work properly. A dirty filter can prevent air from returning to the unit. With less air flow, the coil can freeze.
The Coil
If the filters are fine, go to the evaporator coil and check to see if it is clean. If it is not, it can be fixed with a little time, some cleaner and a plastic brush. Move the brush in the same direction as the metal fins so that they are not damaged. Damaged fins can restrict air flow and cause coil freeze, and the fins can be bent easily.
Returns and Vents
After the filters and the evaporator coil have been cleaned, check for blocked air returns and vents inside the home. Keeping an air return blocked is just as bad as having one with a clogged filter. If air vents are closed, it can also keep air from flowing properly. The cool air will back up into the system, and the warm air in the house cannot be pulled out properly.
Blower
Check the blower. If it is not running, then the unit will keep trying to cool air indefinitely. The blower is what forces the air out of the unit and into the home. If the cool air just sits in the unit, the coil will freeze. If the blower isn't working, or if the other suggestions did not fix the issue, then a repairman will have to be called. More than likely, if it isn't the blower, then the the unit is out of refrigerant and will need to be recharged.
Tags: coil freeze, evaporator coil, then unit
