Central Air Conditioner Quits

Problem: Central air conditioning doesn’t come on, doesn’t cool, or makes noises.

Background: An air-conditioning system pumps heat out of your home. There are two types of central air conditioners: the package system and the split system. The package system has the compressor, outdoor coil, indoor coil, fan, and blower motors in the same housing outside the home; it’s connected to the ducts in the home through an outside wall. The split system has the compressor, fan motor, and coil outdoors. The coil and blower motor (usually art existing furnace blower is used) is indoors and refrigerant lines run between the two sections. Your air conditioner, unless it is used in conjunction with a gas or oil furnace, may also be equipped to provide auxiliary heating with what is called a strip heating system. This system warms the air by blowing it across an electric resistance heating element.

What to do: Many times air conditioners do not start up or work properly because the electrical power is not turned on. Check the circuit breakers or fuses and load-center handles in both indoor and outdoor locations. Study the user’s guide. Make sure that the setting on the thermostat is set to “cool” or “auto” and that the fan switch is set on “auto” or “on” for continuous operation. The setting should be below room temperature. Check the coil outside to be sure that the fan is running. Make sure grilles, registers, and indoor filters are not restricting air flow. (Dirty filters are the most common cause of inadequate cooling and compressor failures.)
Call a technician if you hear new, unusual noises or if the air conditioner is short-cycling (turning on and off rapidly) and not cooling properly. When performing any maintenance, be sure to shut off the electrical power. But otherwise manufacturers suggest you leave the power to the outdoor unit on at all times. To prevent damage to the compressor, do not use the air conditioner until electrical power has been turned on for at least 6 hours.

Special advice: Never use the out door coil as a stand for garden hoses or tools. To assure free air flow, keep the outdoor coil clean and free of grass clippings, weeds, and other debris. Keep fences and shrubs at least 2 feet away from it. Clean and wax the cabinet with car polish to protect the finish. Manufacturers recommend not covering an out door unit with any all-weather cover unless it is a ventilated type or is made of breathable fabric that will allow moisture to evaporate rapidly. A cover that holds moisture may cause more rust and other damage than normal exposure to weather.

Helpful hint: Replace glass fiber throw-away filters when dirty. Clean plastic fiber or foam filters by soaking them in a mild detergent and rinsing them with cold water. Aluminum mesh filters can be washed with detergent and water, but they should be recoated according to the manufacturer’s instructions; they won’t filter dust or dirt as effectively without the adhesive coating.