The heater and air conditioning systems are controlled manually or electronically. The systems differ mainly in the way air temperature and the routing of air flow are controlled. The manual system controls air temperature through a cable-actuated lever and air flow through a vacuum switching valve and vacuum actuators. With Electronic Climate Control (ECC) systems, both temperature and air flow are controlled by the Body Control Module (BCM) through the Climate Control Panel (CCP). There are 2 types of compressors used. The HR-6 compressor, used on Cycling Clutch Orifice Tube (CCOT) systems, is a 6-cylinder axial compressor consisting of 3 double-ended pistons actuated by a swash plate shaft assembly. The compressor cycles on and off according to system demands. The compressor driveshaft is driven by the serpentine belt when the electromagnetic clutch is engaged.
See Figure 1
The V-5 compressor, used on Variable Displacement Orifice Tube (VDOT) systems, is designed to meet the demands of the air conditioning system without cycling. The compressor employs a variable angle wobble plate controlling the displacement of 5 axially oriented cylinders. Displacement is controlled by a bellows actuated control valve located in the rear head of the compressor. The electromagnetic compressor clutch connects the compressor shaft to the serpentine drive belt when the coil is energized.