The air-conditioning system in your car consists of a condenser, a radiator, an evaporator, a compressor, and an accumulator, as well as a network of hoses, switches, and sensors.
It works by taking liquid refrigerant and pushing it through a valve to turn it into a gas, which dramatically lowers the temperature of the refrigerant. In gas form, the refrigerant absorbs the heat from the surrounding air, making the air cold, and the cold air is blown into the vehicle cabin.
Due to the complexity of the A/C system and the special equipment required to service it, all repairs should be done by a qualified technician. However, you should be aware of the basic components of the A/C system and how they work.
The compressor is a big air pump that is usually run from a belt on the engine. The compressor takes in the refrigerant (usually Freon®) as a vapor and compresses it. The gas heats up as it is compressed, resulting in heat and high-pressure vapor. The compressor doesn’t run all the time, so the pulley on the front of it usually has a magnetic clutch that can be turned on and off, as needed.
This piece is usually mounted in front of the radiator. It uses the air that is drawn through the front of the car to lower the temperature of the refrigerant below its boiling point and turn it back into a liquid.
This valve lets the liquid pass at a lowered pressure and causes something called “flash expansion,” which reduces the temperature of the refrigerant and makes it nice and chilly.
The refrigerant is mostly liquid with some vapors and is in a state of low pressure and low temperature. Newer systems use an orifice tube, but they perform the same function.
Moisture in the A/C system is a problem, so most systems have something to keep the system dry. This may be called an accumulator, a drier, or a receiver. It is usually a cylinder mounted somewhere under the hood and in addition to removing moisture it also acts as a reservoir for the liquid refrigerant when it’s not needed.
This component is usually mounted under the dash and attached to a fan. As the cooled liquid/vapor mix runs through the evaporator, the fan blows air over the fins, which transfers warmth from the air to the refrigerant, which then cools the cabin air. The refrigerant warms to boiling and changes back into a gas at low pressure. The low pressure gas is then sent back to the compressor and the process is repeated.