Compressor:

   The compressor is the heart of the air conditioning system. The compressor is a belt driven pump that is fastened to the engine. At the front of the compressor is a magnetic clutch which when given power engages the compressor. It is responsible for compressing and transferring refrigerant gas. As the compressor is the heart of the air conditioning system, it pumps refrigerant in a closed loop through the system. The moving refrigerant moves heat from inside the vehicle to outside the vehicle.

   The A/C system is split into two sides, a high-pressure side and a low-pressure side; defined as discharge and suction. The compressor takes in low-pressure gas coming from the evaporator or in some cases the accumulator and compresses it into a high-pressure hot gas and sends it to the condenser, where it can then transfer the heat that is absorbed from the inside of the vehicle. The compressor discharges this high-pressure gas through its discharge port to the discharge hose.

Condenser:

   This is the area in which heat dissipation occurs. The condenser is usually in front of the radiator and will have much the same appearance as the radiator. The air flowing through the condenser removes heat from the refrigerant that is flowing through it. The condenser takes in hot high-pressure gas and cools it. The gas goes in at the top as a super heated vapor and changes to a sub cooled liquid as it cools. As hot compressed gasses are introduced into the top of the condenser, they are cooled off. As the gas cools, it condenses and exits the bottom of the condenser as a high-pressure liquid.

   In a rear wheel drive vehicle the engines cooling fan supplies the airflow required to draw heat from the condenser. In some cases there will be an auxiliary, electric, cooling fan to provide additional airflow. On front wheel drive cars there will be one, and often times, two electric cooling fans to provide additional airflow through the radiator and condenser.

Evaporator:

   The evaporator is very similar in function to the heater core, except for the fact that it absorbs heat from the passenger compartment instead of supply heat. It is usually mounted under the passenger side dash and mounted to the inside firewall. The low-pressure liquid refrigerant enters the bottom of the evaporator, or a high-pressure liquid that is sprayed into the evaporator by the expansion valve, goes through a rapid evaporation and changes state into a vapor. Its primary duty is to remove heat from the inside of your vehicle but the secondary benefit is dehumidification.

   Just as water condenses on an ice filled glass, water condenses on the evaporator. Airborne contaminants entering the system stick to the wet evaporator and are drained to the outside. Temperature and pressure regulating devices must be used to control its temperature. While there are many variations of devices used, their main functions are the same, keeping pressure in the evaporator low and to keep the evaporator from freezing.

Pressure Regulating Devices:

   The evaporator temperature can be controlled by regulating the refrigerant pressure and flow into the evaporator. There are several ways to do this and the most common are:

Orifice Tube:

   The most commonly used pressure-regulating device is the orifice tube. This is used in most Ford and General Motors cars. It is installed either in the inlet tube of the evaporator or in the liquid line between the condenser and evaporator. The down side of the orifice tube is that it can become clogged with debris and can be costly to replace.

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