DIY Seasonal Maintenance of a Central Air Conditioner

Regular maintenance of a central air conditioner can help keep the system running smoothly for years. It is also the only way to ensure that the system operates at peak energy efficiency.

Some maintenance chores need to be handled by a professional HVAC (heating, ventilation and air-conditioning) contractor, but there are a few important things that you can do yourself. The best time to start a routine is before the start of each cooling season.

Keep the Vents Clear

One chore you can attend to all year long is to make sure that furniture, drapes and the like do not block the the air-conditioning vents and returns in the living area. It is also a good idea to clean the face of the vents whenever vacuuming or dusting.

Clean Off the Outdoor Unit

Most central systems have an outdoor component that houses the compressor and condenser. Its job is to release to the outdoors the heat collected inside the house. A fan circulates air around the condenser coils to cool them. Remove leaves, grass clippings and any other debris from the top of the unit and anything stuck in the fins on the sides. Clear a two-foot space all around the unit to help improve air flow and help it work more efficiently.

Change the Filter

There is a filter located just before the blower unit that removes impurities in the return air. Follow the product manufacturer recommendations for a changing schedule. In most cases, you should change the filter at the start of the cooling season. For warm-weather locations where the air conditioner runs most of the year, change the filter every three months.

Check the unit's manual for the size filter you need. If you don't have the manual, the size of the filter should be marked on the existing filter. Another option is to take the old filter to the store when you buy the new filter.

When installing the new filter, make sure the arrows on the filter frame point in the direction of the air flow.

Air conditioner cleaning. Man checks the filter.
credit: Piotr Adamowicz/iStock/GettyImages
Ductless air conditioners have reusable filters that should be cleaned regularly.

Ductless air conditioner systems, the type that has a unit in each room, usually located near the ceiling, also have filters. Remove the cover to expose the filter. These filters are usually reusable and should be washed with soap and water or vacuumed clean. Be sure they are dry when you replace them.

Check the Thermostat

The Department of Energy recommends setting the air conditioner thermostat at 78 degrees during the summer. That may or may not work for you because comfort is a personal matter, and your overall comfort depends on how well the house is sealed, the local climate and other considerations. But 78degrees is a good place to start. Here are some things to keep in mind when setting the thermostat:

  • For every degree you can raise the AC's thermostat, you can save 3 to 5 percent in energy costs.
  • There's no reason to keep the temperature at a comfortable level if the house is empty most of the day. A programmable thermostat lets you adjust the temperature automatically.
  • Ceiling fans can let you raise the air conditioner temperature 4 degrees without sacrificing comfort. And the fan may be all you need to keep cool on a moderately hot day. By the way, fans cool people by moving air across your skin. If there is no one in the room and the fan is on, you are wasting energy.

Seal the Ducts

This is an important one-time chore. Leaky ducts can waste up to 20 percent of the system's efficiency. Seal the joints with duct mastic and foil-backed tape designed for ductwork. Don't use the fabric tape that is advertised as "duct tape" because it won't hold.

Look for where sections of ductwork are joined together, especially at elbows and turns. Brush the mastic on the joints and cover with the tape. It is also a good idea to make sure that any ducts that run through an unconditioned space, such as an attic, basement or crawl space, are insulated.

Professional Maintenance

Unfortunately, most homeowners can't perform all maintenance tasks themselves. An annual inspection and tune-up by an HVAC contractor can extend the life your system. The pro will check all electrical connections and lubricate the necessary parts. Depending on the system, other tasks the pro will perform include:

  • Checking the condensate drain to make sure it is not clogged, and clean it if it is clogged. Air conditioners produce condensation that must drain away from the system. A clogged drain line can damage the equipment.
  • Adjusting the blower motor if necessary
  • Checking and adjusting the refrigerant level in the system
  • Cleaning the evaporator and condenser coils. Dirty coils reduce the system's efficiency and shorten the life of the unit.

Some contractors offer service contracts that usually means a technician is on call 24/7 should a problem arise. Make sure you know what is in the contract before agreeing to it. But having a relationship with a contractor gives you the peace of mind of having a number to call in case of an emergency.