There are several things you can do yourself to keep a central air conditioner, heat pump or a window air conditioner running at peak efficiency. Because the furnace air handler (blower) is also used for central air conditioning, maintaining it may also decrease your heating bills.
The two key factors to keep an air conditioner running most efficiently are making sure it has the proper amount of airflow over the indoor and outdoor coils and keeping the coils clean. Clean coils transfer heat more efficiently to the air blowing over them so the compressor has to run less to produce the same amount of cooling output.
First, remove any items, branches, leaves, etc., which are resting against the outdoor condenser unit housing. These items may interfere with the airflow over the coils inside the unit. Clean off any leaves, pine needles, etc., from the top grille. They may blow off on their own when the unit starts running this spring, but it does not hurt to manually remove them.
Before doing any internal maintenance on a central air conditioner, always switch off the power to the unit at the circuit breaker panel box. You may also find a large switch near the outdoor unit. Usually, you have to open the switch door and pull a connector bar from it with its plastic handle. If you are at all unsure about how to do this, DO NOT attempt it yourself.
Look down inside the outdoor unit for old leaves and debris which may have accumulated during winter. These not only can reduce efficiency, but they can accelerate corrosion of the steel housing. Remove the screws from the side access panel to remove it. Reach in and clean out the debris.
Be careful not to damage the fragile fins on the coils. If you do bend some together, use the tip of a knife to separate and straighten them. It is not important for all of them to be perfectly straight. There just needs to be a gap for air flow between them. Inexpensive plastic fin combs are available to space them more accurately if you chose.
When reassembling the access panel, be sure to adequately tighten the screws. If the screws are not tight, air may be sucked in around the loose panel instead of through the coils. This reduces efficiency. Even if you do not have to clean out any debris, make sure all the exterior panel screws are tight.
Move indoors to the air handler that circulates the air throughout your house. If you have not changed the filter for the past two months, change it now. A dirty air filter actually cleans better than a new one, but it may create too much airflow resistance for maximum cooling efficiency.
Remove the screws from the side panel to gain access to the cooling coils. Use your vacuum cleaner brush attachment to clean off any dust. You may have to gently brush it first with a hand brush to dislodge any dirt. Dust may accumulate on the damp indoor air conditioning coils and stick when it dries.
As with the outdoor access cover, make sure the screws are tight on the indoor air handler. While you are around the ductwork, seal any gaps at joints with tough Gorilla Tape, T-Rex tape or aluminum foil tape.