Compressor HVAC: Description and Operation

V5 Compressor Description

General Description
Different vehicles with V5 compressors may exhibit differences in mounting and installation, but overhaul procedures are similar. Before removing the compressor or performing on-vehicle repairs, clean the compressor connections and the outside of the compressor.

CAUTION: After removing a compressor from the vehicle for servicing, drain the oil by removing the oil drain plug. Also drain the oil from the suction and the discharge ports to insure complete draining. Measure the amount of oil drained, and record that amount. Discard the used oil and add the same amount of new Polyalkaline Glycol (PAG) refrigerant oil to the compressor.

The compressor has been removed from the vehicle unless otherwise indicated.
Clean tools and a clean work area are important for proper servicing. Keep dirt and foreign material from getting on or into the compressor parts. Parts that are to be reassembled should be cleaned with trichloroethane, naphtha, stoddard solvent, kerosene or equivalent solvents. Dry the cleaned parts with clean dry air. Use only lint-free cloths to wipe the parts.

Description of Operation
The V5 is a variable displacement compressor that can match the automotive air conditioning (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 bellows-actuated control valve located in the rear head of the compressor. The control valve 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 wobbleplate 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.