Key Tasks

In the outside portion of the unit, a fan moves air through a condenser coil, where the refrigerant is liquefied and sent to the evaporator coil.

Most room air-conditioners are permanently lubricated. Routine upkeep consists of keeping their filters and coils clean. When a unit refuses to run, make sure its filter is clean and that the power cord is plugged in. Check the main service panel for a blown fuse or tripped circuit breaker. Don't restart a room air-conditioner for 5 minutes after it kicks off, so that built-up heat can dissipate first.

If the unit cycles on or off too often or otherwise runs erratically, suspect thermostat problems. Often this means that the thermostat sensor has been knocked out of position. The sensor should be near the coil, but not touching it. Adjust it by carefully bending the wire. If you hear a gurgling noise, or if water drips from the front panel, shut off the power and check with a level to make sure the cabinet's outer section slopes toward its condensate drain.

Some types of filters are vacuumed; others should be washed or replaced. Clean or change the filter every two to three weeks during the cooling season.

Every month, check the condenser coil and intake vents for obstructions, such as leaves or dirt. Hose out this part of the unit every spring.

Also, check the condensate drain outlet. If it is plugged up or the unit is not properly pitched away from the house, condensation can't run out.