GMC 1990 Light Truck Repair Manual page 45

V5 AIR CONDITIONING COMPRESSOR
SUBJECT
Description..................................................................................................................................................................... 1B2- 1
Theory of Operation.................................................................................................................................................. 1B2- 1
Minor Repair to the Compressor..................................................................................................................................1B2- 2
Clutch Plate and Hub Assembly Replacement........................................................................................................ 1B2- 2
Pulley and Bearing Assembly Replacement...........................................................................................................1B2- 4
Clutch Coil Replacem ent.......................................................................................................................................... 1B2* 7
Pressure Relief Valve Replacement......................................................................................................................... 1B2- 7
High-Side Pressure and High-Side Low Pressure Cutoff Switches Replacement.............................................. 1B2- 8
Control Valve Replacement......................................................................................................................................1B2- 9
Major Repair to the Compressor..................................................................................................................................1B2- 9
Shaft Seal Replacement............................................................................................................................................1B2- 9
Front Head Seal, Rear Head Gasket, Rear Valve Plate, Suction Reed Plate and
Cylinder to Rear Head Seal Replacement.............................................................................................................1B2-10
Leak Testing................................................................................................................................................................... 1B2-12
Specifications................................................................................................................................................................. 1B2-13
Special Tools................................................................................................................................................................... 1B2-14
V5 AIR CONDITIONING COMPRESSOR
THEORY OF OPERATION
The V5 is a variable displacement compressor that can
match all air conditioning demands under all conditions
without cycling (figure 1). The basic compressor mecha­
nism is a variable angle wobble-plate with five axially ori­
ented cylinders. The center of control of the compressor
displacement is a bellows actuated control valve located in
the rear head of the compressor that senses compressor
suction pressure. The wobble-plate angle and compressor
displacement are controlled by the crankcase-suction pres­
sure 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; no
crankcase-suction pressure differential; and the compres­
sor will have maximum displacement. When the A/C capac­
ity 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 con­
trolled by a force balance on the five pistons. A slight eleva­
tion of the crankcase-suction pressure differential creates a
total force on the pistons resulting in a movement about the
wobble-plate pivot pin that reduces the plate angle.
V5 AIR CONDITIONING COMPRESSOR 1B2-1
SECTION 1B2
CONTENTS
DESCRIPTION
The crankcase-suction bleed is routed through the rotat­
ing 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, rerouting it to
the crankcase where it can lubricate the compressor mech­
anism.
Up to 113 g (4 oz.) of oil can collect in the crankcase.
Therefore, it is important when replacing a compressor that
the oil in the old compressor crankcase be drained through
the drain plug and measured (discard after recording
amount).
All replacement compressors will be shipped with 227 g
(8 oz.) of oil in the crankcase. The oil must be drained and
retained. Then replace the oil in the same amount as previ­
ously recorded from the old compressor. Refer to " Specifi­
cations."
IDENTIFICATION
An identification label attached to the compressor pro­
vides the name of the manufacturer, model number and
build code.
When servicing the V5 compressor, keep dirt and foreign
material from getting on or into the compressor parts and
system. Clean tools and a clean work area are important for
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