Because an air conditioner uses large amounts of electricity, the cool air it delivers is costly. To get your money’s worth, seal or weatherstrip all air leaks and gaps around the unit and in the room (see Weather stripping). If you live in an area of high air pollution, you should have a serviceman give the unit a chemical or steam cleaning at least once a year. Caution: Before performing any operations, turn off and unplug your unit.
If performance falls off, inspect the filter. Clean or replace it if clogged by dust. In most units the filter is on the room side behind a grille. The filter lifts out, or it can be removed after a front panel is taken off. Remove any screws or release any latches holding the panel and pull it from the unit.
Wash a reusable filter in detergent and water, rinse it, and reinstall it. If there is a break in the filter, dust may have collected on the evaporator fins. Vacuum the fins clean. But be careful not to cut yourself or damage the fins.
If the cabinet is not tilted toward the outdoors, water may drip into the room. Tilt it so that the outdoor side is slightly lower than the indoor side.
The smell of oil or tobacco calls for professional cleaning. A musty odor means clogging of the drain hole under the barrier between the evaporator and compressor or of the channel under the evaporator. Remove the screws and take off the grille to get at the hole or the gap. (On some models you may have to pull the unit partly out of its cabinet.) Clean the hole with a bent wire hanger or clean the gap with a bulb baster filled with water.