Pontiac FIREBIRD 1972 Service Manual page 93

1A-34 1972 PONTIAC SERVICE MANUAL
SWASH PLATE
An angular shaped member (swash plate) is located near
the center of the compressor. The swash plate changes the
rotating action of the shaft to provide a reciprocating
driving force to each of the three pistons. This driving
force is applied, through the shoes and balls, to the mid-
point of each of the double end pistons. The swash plate
has two angular faces ground smooth and parallel to per-
mit smooth sliding of the shoe discs.
The plate is a .0005"
-
.001OV press fit into the 3/4" diame-
ter shaft and is positioned by a woodruff key located in the
shaft.
SUCTION CROSS-OVER AND COVER
Since the pistons are double-acting, low pressure vapor
from the cooling coil must be supplied to both ends of the
compressor and pistons.
The inlet (suction) port on the rear head of the compressor
is connected by a hose to the outlet side of the evaporator
(cooling coil). A fine mesh suction screen is located in the
low pressure inlet cavity of the rear head. Its purpose is
to trap any material (larger than the mesh size) that would
damage the compressor mechanism.
A flat rectangular cavity is cast into the outer face of the
front and rear cylinder block halves. The edges of this
cavity are machined into a dovetail shape to retain a rec-
tangular suction crossover cover. This cover and gasket
form a passage for the low pressure vapor to flow from the
rear head of the compressor to the front head and thus
apply suction refrigerant to the pistons and cylinders at
the front of the compressor.
The sides of the cover seal it to the suction crossover
cavity and the narrow ends of the cover form a seal with
the underside of the suction and discharge valves when
they are assembled to the cylinder heads.
DISCHARGE CROSS-OVER TUBE- PRODUCTION
TYPE
The double-acting pistons also produce high pressure va-
por at both ends of the compressor. The outlet (discharge)
port for the high pressure vapor is located in the rear head
of the compressor.
A discharge vapor tube is used to connect the front head
discharge cavity to the rear head discharge cavity. This
tube has cylindrical ends that are spun into holes in the
front and rear cylinder head halves to provide a vapor
tight joint. The center of this tube has a flattened cross-
section to provide clearance between the swash plate and
tube.
When the pistons in the front end of the cylinder are on
their compression stroke, the high pressure vapor is
caused to flow into the discharge cavity in the front head,
through the discharge tube and into the rear head dis-
charge cavity. This vapor combines with the high pressure
vapor produced by the pistons in the rear cylinder head
during their compression stroke and flows out the com-
pressor discharge port.
DISCHARGE CROSS-OVER TUBE- SERVICE TYPE
The purpose, function, and design of the service discharge
tube are the same as those for the production-type tube
with the exception of shouldered sleeves located in both
ends of the service tube. These shoulders provide a surface
for the O-rings and compression bushings. Since the pro-
duction discharge tube is vapor sealed to the front and rear
cylinder heads by spinning in the ends of the tube, equip-
ment to perform this spin in operation during service oper-
ations would not be economical. Therefore, it if should be
necessary to separate the cylinder halves during a service
operation, a service-type discharge tube should be used
when reassembling the mechanism.
PRESSURE RELIEF VALVE
The compressor is fitted.with a high pressure relief valve.
If the discharge pressure ever exceeds approximately 440
psi, the relief valve opens automatically to relieve the
pressure and closes again when the pressure recedes.
Opening of the relief valve will be accompanied by a loud
popping noise and perhaps the ejection of some oil with
the refrigerant. Any condition that causes this valve to
open should be corrected immediately.
OIL TEST OUTLET
An oil test outlet is located on the underside of the com-
pressor shell. This outlet is a screw having a hole drilled
lengthwise through its center to the head which indexes
with a hole drilled crosswise just above the head. This
allows oil to enter the drilled holes and be emitted when
the screw is loosened.
The proper method of checking oil level is outlined under
CHECKING COMPRESSOR OIL LEVEL AND ADD-
ING OIL.
SHELL
The shell of the compressor has a mounting flange on the
front end and four threaded screws welded to the outside
at the rear. An oil sump is formed into the bottom of the
shell, with a baffle plate over the sump on the inside of the
shell. There is an oil charging screw and gasket (which
also serves as an oil test outlet) in the wall of the shell.
The compressor serial number is located on a plate on top
of the compressor. This number should be included in all
reports, claims or correspondence concerning the com-
pressor. The compressor part number is also shown on the
serial number plate.