A/C Compressor Controls

When the Ignition Switch is in RUN, battery voltage is applied through Fuse 20 to the A/C Select Switch on the A/C Control Panel. When the A/C Select Switch is pressed voltage is applied to terminal 3 of the Evaporator Temperature Regulator. The Evaporator Temperature Regulator applies voltage from terminal 2 to the Compressor Clutch through the Refrigerant Pressure Switch.

The Refrigerant Pressure Switch will disengage the Compressor Clutch when refrigerant pressure rises above 30.0 bar (435 psi) or when a lose of refrigerant brings the pressure below 1.5 bar (21.8 psi). The Evaporator Temperature Sensor signals the Evaporator Temperature Regulator to deenergize the Compressor Clutch when evaporator temperature is low enough that freezing may result.

Clutch Diode
Whenever the Compressor Clutch is de-energized, the collapsing magnetic field induces a voltage in the winding. The Clutch Diode provides a path for the resulting current.