Evaporator coils are used in both air conditioners and heat pumps as filters for the heating or cooling system. It's recommended that the evaporator coils inside of air conditioners – especially central air conditioners – should be cleaned on a regular basis.
Knowing how something works is the first step toward knowing how to fix it, or in this case, clean it. Central air conditioners pull the air from inside the house and filter it through the evaporator coils. These coils cool the air that passes through them, and then that air is moved back out into the house. This cycle repeats itself until the system is turned off.
The air that goes through the evaporator coils carries dirt, dust and anything else that gets into it. Particles can build up in the evaporator coils and clog the system over time. A call to the repairman may be avoided if you know how to clean the evaporator coil of a central air conditioner.
The evaporator coil is located above the furnace in the main duct. In some cases the evaporator coils are not accessible, but if the main duct has a foil-wrapped insulation and is not in a sheet metal box, then it can be cleaned. Remove the insulation at the front of the main duct – and do it carefully, as it will have to be replaced after the cleaning is finished.
Behind the insulation will be a metal plate that can be unscrewed and will also need to be carefully removed. To remove dust and dirt from evaporator coils, use a firm brush. Evaporator coils can be slid forward, but this isn't recommended as it can cause damage to the air conditioner if pipes near the coils are bent. A tablespoon of bleach can keep fungus from growing in the trays beneath the evaporator coils. Once you've done those two things, replace the insulation and the metal plate. Check for leaks by turning the system back on, and cover any leaks with duct tape.