An air conditioner coil is the part that turns a liquid chemical such as Freon into a gas and absorbs heat while creating cool air. The coil functions as a heat exchanger, because it draws out heat and creates the cool air that blows out of the air conditioner.
Air conditioner coils are also called evaporator coils or indoor coils and are mainly made up of copper tubes with aluminum fins. They are often described as the cold coil because they supply the cold indoor air by absorbing heat from the air that is blown into the unit.
Evaporator coils can freeze up if they are not properly cleaned and maintained. There is a second coil on an air conditioning unit that is called the condenser or outdoor coil, often referred to as the warm coil, because it rejects warm air and blows it back outside.
It is important to keep the coils in an air conditioning unit clean, because when they are dirty, they cannot properly transfer heat, resulting in higher energy consumption and higher electric bills. Dirty coils can also lead to reduced cooling capacity, increased pressure and higher temperatures in the unit, which can result in equipment failure.