An air conditioner works by removing heat from the interior of the building and venting it outside. The air conditioning system consists of a compressor, condenser coil, evaporator coil, blower fan, condenser fan, thermostat and related electrical circuitry and tubing. The evaporator coil provides the cold air while the condenser releases the heat.
Evaporator Coil Location
The evaporator coil is inside the home, usually just downstream of the blower fan in either the attic or a utility closet. It is accessed through a service port in the ductwork, or an opening may have to be cut through the side of the duct for first-time access.
The evaporator coil consists of copper or aluminum tubing about 1/3 inch in diameter that curves in a serpentine fashion through a grid of metal cooling fins. The fins help the tubing absorb the heat from the air flow and cool the air flowing downstream into the air ducts. The fins are made of aluminum or copper, as both absorb and release heat rather quickly.
Poor Coil Maintenance
Dust, dirt and pollen get past the air filter over time and collect on the evaporator coil. The coil is moist with condensation, so impurities stick to the coil and provide a collection point for more dust and particles to accumulate. The contaminants reduce the efficiency of the heat transfer and also provide a breeding ground for mold and corrosion to form. Corrosion will eventually cause the evaporator coil to leak, requiring replacement. Excessive dirt will block the air flow enough to trap too much cold air around the evaporator, causing it to ice up. Icing can damage or destroy the evaporator if left unchecked.
Improper servicing of the evaporator coil may pierce the tubing, making replacement necessary. Even a very small pinhole will allow the refrigerant to escape making the air conditioner inoperative.
Ideal Life Expectancy
A properly serviced and maintained home air conditioning compressor should last 10 to 15 years. The evaporator coil should be replaced along with the compressor as the two must be properly matched to provide efficient cooling. Leaving an old evaporator coil in place while replacing the compressor will probably make the unit less efficient, and might leave undetected corrosion in place.