Compressor

Compressor
The Saturn compressor is a variable displacement rotary vane type pump. The rotor assembly houses five lightweight vanes that extend outward contacting the cylinder wall creating the compression area. The compressor has an internal control valve that allows it to change its pumping capacity or displacement, reacting to heat loads on the air conditioning system. The range of displacement can vary from 10% (8 cc) to 100% (110 cc). Due to the force of the torsion spring acting on the rotating plate the compressor's natural or resting state is at minimum displacement.
The compressor performs two main functions. It compresses the low pressure refrigerant vapor from the evaporator into a high pressure high temperature vapor, and pumps compressor oil through the A/C system.

Compressor Clutch
The magnetic clutch transmits the engine power to the compressor when the A/C button is depressed. The clutch assembly consists of a drive plate, pulley and field coil. The drive plate is splined to the compressor shaft. The pulley and bearing assembly is pressed on the compressor hub, and the field coil is mounted to the compressor body. When current flows through the field coil, the drive plate is pulled into the pulley by electromagnetic force.

When the field coil is not energized the drive plate separates from the pulley and the compressor stops. A diode is used to protect electrical circuits from voltage spikes. The diode is located in the underhood junction block.

Pressure Relief Valve
Mounted in the front head is a high pressure relief valve. To protect the A/C system from high pressure in the event of an electrical control system failure the valve will begin to open at about 3654 kPa (530 psi). As system pressure is reduced the valve will reseat at about 2930 (425 psi). If the valve even opens it must be replaced.