How do I select a good HVAC contractor to fix my old air conditioner? Is there any simple maintenance I can do myself?—Barb

Finding a good contractor to repair or replace an old air conditioner is important because you want your system to keep running for a long time after the work is done.

When selecting a contractor, first check with your relatives and friends for recommendations. When a contractor gives you a list of references, call each one.

You also can check with the Air Conditioning Contractors of America Association, Inc., and the Sheet Metal and Air Conditioning Contractors’ National Association.Reputable contractors will belong to one or both of these organizations, and you can search online for a list of members in your area.

For a repair job, get quotes from at least three contractors. Be wary if they immediately want to replace the system with a new one. They should determine the problem and also provide a quote for repair.

Take your time to evaluate the quotes and recommendations, even though your family might be uncomfortably warm for several days.

Maintenance tips

There are several maintenance tasks you can do yourself each summer to keep your air conditioner running efficiently, but don’t eliminate regular professional service even when it seems to be running properly.

Having adequate air flow through the outdoor condenser coils is imperative for good efficiency and a long life. Make sure there is at least 3 feet of clearance around the housing where the coils are exposed to the outdoor air.

If you notice some of the heat transfer fins on the coils are bent over and touching so air cannot flow between them, separate them with the tip of a scraper, but don’t flex them too much or they may break off. Make sure all the screws on the outdoor and indoor sheet metal housing are tight. Tape any leaky supply or return duct joints.

If your unit has a low-cost, standard fiberglass filter, replace it often. Though more expensive, a filter with a MERV 11 rating or MERV 8 at the minimum is best.

JAMES DULLEY is a nationally syndicated columnist who writes on energy efficiency and do-it-yourself energy topics.