Tune Up a Central AC Unit

Extend the life of a central AC unit with these basic maintenance chores and preventive measures to keep the system working most efficiently.

By Gene And Katie Hamilton

Tune Up a Central AC Unit

A central air conditioning system runs trouble-free most of the time, but there are a few simple jobs you can do to keep it working most efficiently. That teamed with periodic professional maintenance to check the compressor and refrigerant levels will help you realize the most cooling for your energy dollars. Here's what you can do to extend the life of the unit and keep it healthy and working efficiently.

Trim back shrubbery around the unit.

Keep the area around the air conditioner's outdoor condenser clean. Trim back any bushes or weeds that grow around the unit so nothing obstructs the passage of air through the condenser coil.

Change its filter at least once a month.

Most central air conditioners distribute cool air through a house with the same air handling system that the heating system uses. The air conditioner uses the furnace blower to move the cool air throughout the house. This air must pass through the furnace filter so it's just as important to keep this filter clean whether it is cooling or heating season. To get the most out of the air conditioner, change the furnace filter regularly, at least once a month.

This filter is usually located in the base of the furnace in the return air duct. Dirty handprints left by a previous owner or serviceman on the side of the cold air return duct or air conditioner blower unit are a good tip-off to the filter's location. If you can't find it, consult your owner's manual.

If your furnace has a permanent filter, which is usually a frame with a washable foam filter stretched over it, remove and wash the filter in warm water and a mild detergent. Then allow it to dry on a flat surface before reinstalling it on the frame. If your furnace has a fiberglass filter in a paper frame, measure the filter or read the size marked on the frame and buy a couple of replacement filters. It's a good idea to keep your eyes open for "filter sales" and always have a supply on hand.

Check the drain lines during high humidity.

One of the chief functions of a central air conditioning system is to dehumidify the air. On humid days the cold "A" coil in the furnace will condense a lot of water from the air, so check that the drain line serving the drip pan under the evaporator coil is not clogged. Remove the inspection cover to find the pan which is located under the coil usually in the upper portion of the furnace. Clean the drip pan carefully so the drain will not clog later in the season. When everything is clean, replace the inspection cover.

Clean the evaporator coil at least once a season.

The evaporator coil should be dry when you clean it so do this maintenance before you turn on the air conditioning for the season. The evaporator coil is triangular in shape and usually located in the top of the furnace in the main duct. It is usually accessible through an inspection cover on the side of the furnace. Use the crevice tool of a vacuum to suck up the dirt and dust lodged between the coil fins.

To blow loose dirt and lint from the coil fins, reverse the hose on the vacuum so that it blows outward or use a hair dryer. Aim the hose or hair dryer at the outside of the coil to dislodge the particles that have been blown into the coil from underneath. Straighten any bent fins with a small screwdriver; be careful not to damage the core tubing. You can also purchase an inexpensive fin comb designed to straighten these aluminum fins.

Get a programmable thermostat

Consider replacing your thermostat with a programmable unit that let's you adjust the temperature in your house to your lifestyle automatically. The unit raises the thermostat setting when no one is home and lowers it before everyone arrives back home. It works in the same manner during the heating system to lower the thermostat setting when no one is home and raise it when heat is needed.

Cost to Install a Programmable Thermostat

Cost to Install a Self-learning Thermostat

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