Compressor HVAC: Description and Operation

V5 Compressor

General Description

Vehicles using the V5 compressor may have differences between installations in the mounting brackets, the drive systems, the pulleys, the connections, and the system capacities. Basic overhaul procedures are similar between the compressors used on different vehicles.
When servicing the compressor, keep dirt and foreign material from getting on or into the compressor parts and the system. Clean tools and a clean work area are important for proper service. The compressor connections and the outside of the compressor should be cleaned before undertaking any on-vehicle repairs and before the removal of the compressor. The parts must be kept clean at all times. Any parts that are to be reassembled should be cleaned with trichloroethane, naphtha, stoddard solvent, kerosene, or equivalent solvents and dried with dry air. Use only lint-free cloths to wipe the parts.
The operations described are based on bench overhaul with the compressor removed from the vehicle, except as noted. They have been prepared in the order of accessibility of the components. When a compressor is removed from the vehicle for servicing, the amount of oil remaining in the compressor should be drained, measured, and recorded. This oil should then be discarded and new polyalkaline glycol (PAG) refrigerant oil added to the compressor.

NOTE: The oil drain plug must be removed and the oil drained through the plug opening to insure complete draining of the oil from the compressor.

Description of Operation

The V5 is a variable displacement compressor that can match the automotive A/C demand under all conditions without cycling. The basic compressor mechanism is a variable angle wobble-plate with five axially oriented cylinders. The center of control of the compressor displacement is a billows-actuated control valve located in the rear head of the compressor that senses compressor suction pressure.
The wobble-plate angle and the compressor displacement are controlled by the crankcase suction pressure differential. When the A/C capacity demand is high, the suction pressure will be above the control point. The valve will maintain a bleed from crankcase to suction. With no crankcase suction pressure differential, the compressor will have maximum displacement.
When the A/C capacity demand is lower and the suction pressure reaches the control point, the valve will bleed discharge gas into the crankcase and close off a passage from the crankcase to the suction plenum. The angle of the wobble-plate is controlled by a force balance on the five
pistons. A slight elevation of the crankcase suction pressure differential creates total force on the pistons resulting in a movement about the wobble-plate pivot pin that reduces the plate angle.
The compressor has a unique lubrication system. The crankcase suction bleed is routed through the rotating wobble-plate for lubrication of the wobble-plate bearing. The rotation acts as an oil separator which removes some of the oil from the crankcase suction bleed, re-routing it to the crankcase where it can lubricate the compressor mechanism.