GMC 1976 ZEO 6083 Maintenance Manual page 56

A two-row ball bearing is pressed into the pulley
hub and held in place by a retainer ring . The entire
pulley and bearing assembly is then pressed over the
front head of the compressor and secured by a re-
tainer ring .
Clutch Coil
The coil is molded into the coil housing with a
filled epoxy resin and must be replaced as a complete
assembly . Three protrusions on the rear of the hous-
ing fit into alignment holes in the compressor front
head. A retainer ring secures the coil and housing in
place. The coil has 3 .85 ohms resistance at 80°F .
(26.7°C .) ambient temperature and will require no
more than 3.2 amperes at 12 volts D.C . Since the
clutch coil is not grounded internally, a ground lead
is required as well as a "hot" lead . This will be dis-
cussed in greater detail in the Electrical Component
discussion in this section.
Shaft Seal
The main shaft seal, located in the neck of the
compressor front head, consists of the seal assembly
with its ceramic seal face in a spring loaded cage . An
"O" ring seal, located within the ceramic seal, pro-
vides a seal to the shaft surface. The contact surface
of the shaft seal seat is finished to a high polish and
must be protected against nicks, scratches and even
fingerprints . Any surface damage will cause a poor
seal . An "O" ring, located in an internal groove in
the neck of the front head provides a seal with the
outer diameter of the seal seat . A retainer ring, ta-
pered side away from the seat, secures the seat in
place. The hub and armature plate must be removed
to gain access to the seal . A shaft seal kit contains all
necessary replacement parts for field service.
After removing the clutch drive, pulley-bearing
and coil housing assemblies, the rear head and inter-
nal mechanism (figure 10) may be removed from the
compressor shell . Four threaded studs, welded to the
compressor shell, locate the rear head and four lock
nuts secure it in place.
Rear Head
The rear head (figure 11) has a machined cavity
in the center for the oil pump gears. This cavity, in
all compressors, is machined so that the eccentricity
of the bore is approximately .042 inch to the LEFT
of the centerline of the cavity . The counterclockwise
rotation compressor used in some other systems has
the eccentricity machined approximately .042 inch
to the RIGHT of the cavity centerline . A small diam-
eter hole is drilled in the head between the two. The
unit number is stamped on a plate attached to the
counterclockwise rotation head and a decal arrow
indicates the direction of rotation .
Mainshaft
The central mainshaft, driven by the clutch-pul-
ley when the coil is energized, extends through the
front head to the rear head and oil pump cavity of
the compressor. The shaft revolves in needle roller
bearings located in the front and rear halves of the
cylinder assembly . 3/16" internally drilled passage
extends through the shaft from the rear oil pump
cavity to the shaft seal cavity in the front compressor
head . Four .078 inch holes, drilled at 90° to the main
passage, direct oil under pump pressure to the shaft
seal surfaces, thrust bearings and shaft-cylinder bear-
ings .
Axial Plate
AIR CONDITIONING SYSTEM
1- 39
The axial plate is an angular shaped member
pressed onto the mainshaft forming the mainshaft
and wobble plate assembly (figure 11). A woodruff
key prevents movement of the plate around the shaft.
Location of the plate on the shaft is factory set and
must not be changed. The very smooth angular faces
of the plate are ground to be parallel within .0003
inches of each other. The plate changes the rotating
action of the shaft into the reciprocating driving
force for three pistons . The driving force is applied,
through the drive balls and ball seats (shoe discs) to
the midpoint of each of the double end pistons.
Cylinder Block
The cylinder block consists of a front and a rear
half. Three piston bores are line bored in each half
during production to assure proper alignment and
parallelism. The two halves must be serviced as an
assembly to assure correct relationship of parts.
Pistons
The cast aluminum double end pistons (figure
11), have special grooves to receive teflon piston
rings. A notch in the casting web of each piston
identifies the end of the piston which should be posi-
tioned toward the front end of the compressor . A
spherical cavity is located on both inner faces of each
piston to receive the piston drive balls.
Drive Balls
The hardened steel drive balls have a micro-fin-
ish. They are manufactured to a .0001 inch spherical
tolerance and a .6248 - .6250 inch diameter toler-
ance .
Shoe Discs
The bronze shoe discs have one flat side, which
contacts the axial plate, and one concave surface into
which the drive ball fits . Ten discs are provided in