Compressor Operation; Compressor Fittings Assembly - Pontiac FIREBIRD 1972 Service Manual

CUSTOM AIR CONDITIONING 1A-39
These parts are formed into an assembly by molding a
frictional material between the hub and the rim. The
power element ring is embedded in the forward face of the
assembly, between the outer rim and the inner hub.
A two-row ball bearing is pressed into the hub of the
pulley and held in place by a retainer ring. This pulley and
bearing assembly is pressed over the front head of the
compressor and held in place by a retainer ring.
CLUTCH COIL
The clutch actuating coil is molded into the coil housing
with a potted epoxy resin; therefore, the coil and housing
are replaceable only as a complete assembly. The coil has
3.85 ohms resistance at 80°F. (surrounding temperature)
and should not demand more than 3.2 amperes at 12 volts
D.C.
Three protrusions on the rear face of the coil housing fit
into alignment holes in the front head of the compressor.
When the coil and housing assembly is aligned and en-
gaged with the front head (and indexed with the protru-
sions), it is secured in place by a retainer ring.
COMPRESSOR SHAFT SEAL
A replaceable seal is used at the front of the compressor
to seal the air conditioning system from atmosphere when
the compressor is operating or at rest, regardless of pres-
sures in the compressor.
Components of the seal located in the neck of the front
head of the compressor (Fig. 1A-33) are the retaining ring,
the small O-ring, the compressor spring-loaded shaft seal,
SHAFT SEAL SEAL SEAT SEAL SEAT HUB A N D ARMATURE
ASSEMBkY
I
RJTAlNER PLATE PSSEMBLY KEY
I
Fig. 1A-33 Cross Section-Compressor Shaft Seal Area
the ceramic seal seat and the large O-ring. The seal indexes
with two flats machined on the compressor shaft and turns
with the compressor shaft.
A spring in the shaft seal assembly holds the seal against
the seal seat, which is held stationary in the neck of the
compressor front head by a retainer ring. The tapered side
of the retained ring should be assembled toward the front
of the compressor. Because of the constant pressures in-
side the compressor, the seal surfaces must be protected
against any damage, such as scratches and nicks (even
finger markings may cause surface damage) to prevent oil
and/or refrigerant leaks past this seal.
The small O-ring seals between the shaft and the seal, and
the large O-ring seals between the seal seat and the com-
pressor front head.
Service shaft seal parts are supplied in a complete kit
containing all necessary replacement parts.
COMPRESSOR OPERATION
Current flowing through the coil creates a magnetic force
which flows through the pulley to draw the armature plate
(forward of the pulley assembly) rearward toward the
pulley. As the armature plate moves toward the pulley, it
contacts the pulley shaft face (which rotates freely about
the compressor shaft).
The design of the clutch and coil is such that maximum
magnetic holding force is obtained to magnetically lock
the armature plate and pulley together as one unit. Since
the clutch hub is pressed on and keyed to the compressor
shaft, the compressor shaft will then turn with the pulley.
When ambient temperature is below 32°F. or the control
panel system selector lever is set at OFF (also VENT or
HEATER on B Series) or the Vent-Normal switch (except
B Series) is turned to VENT, the electrical circuit to the
compressor clutch is opened and the magnetic pull on the
clutch no longer exists. The armature plate to driven ring
actuating springs will then pull the armature plate away
from the pulley and the plate loses contact with the pulley.
With the clutch released, the pulley rotates freely on its
bearing. In this condition, the compressor shaft does not
rotate.
It may be noted that if the air conditioning system was in
use when the engine was turned off, the armature plate
may remain'in contact with the pulley, due to residual
magnetism. This will cause no trouble, as the armature
plate and pulley will separate as soon as the engine is
started.
COMPRESSOR FITTINGS ASSEMBLY
The mumer and compressor fittings assembly (Fig. 1A-
34) contains an open passage into the compressor frc-m the
evaporator (low pressure) and an open passage from the
compressor to the condenser.