Dear Jim: My central air conditioner was serviced last year and I don’t think it needs it again, but I want to do some simple maintenance myself this year. What can I do to it myself to lower my cooling bills? – Ron H.

Dear Ron: If your air conditioner seems to be working properly and it was serviced just last year, there really is no need for another expensive service call this spring. Other than checking the refrigerant pressures, you can check many of the same items as the technician does.

It helps to understand how an air conditioner works when doing your own checkup. The outdoor compressor, through phase change (gas to liquid) heats the refrigerant warmer than the outdoor air. It then gives off this heat through the condenser coils and fan outdoors. The refrigerant flows indoors, changes back to gas, and chills the coils in the indoor blower.

With all this transferring of heat from hot outdoor coils and cool indoor coils, the key to maintaining high efficiency is adequate airflow over the various sets of coils. If either the outdoor or indoor coils do not receive the proper amount of air flow, your monthly utility bills will be higher.

Starting outdoors, make sure there is nothing blocking the airflow through the condenser coils. Obstructions include shrubs, which have grown too close, garden tools or toys stored against the outdoor unit or leaves and debris inside the outdoor cabinet.

If you see many leaves inside the unit, switch off the circuit breaker to it and remove the outdoor cover. Remove the debris you find inside. While the cover is off, check for any bent fins on the coils. These can get damaged if children push sticks in through the wire grille. Bent fins can be straightened with the tip of a knife.

When you replace the cover, make sure to replace all the pieces and securely tighten all the screws. Even if you did not remove the cover, check the tightness of all the screws. If part of the cover is missing or the screws are loose, the condenser fan will draw air in the gaps instead of through the coils as it is designed to do.

With the electricity still turned off, remove the indoor cover over the blower motor and evaporator coils. Using a soft brush attachment, vacuum off any dust and then wipe them down with a damp cloth. Just a thin layer of dust can reduce the heat transfer effectiveness.

While the cover is off, check the drain hole in the drip pan under the evaporator coils. This pan catches the water as the air conditioner dehumidifies the air. If the hole to the floor drain is clogged, the moisture will just get back into the indoor air again.

Change the filter or service the air cleaner in the return air duct. I have seen them so clogged with dust and pet fur that very little air gets through. Replace the cover and tighten all the screws securely.

Send inquiries to James Dulley, 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit www.dulley.com.