Superheat Switch; Rear Head, Oil Pump And Valve Assemblies - Chevrolet 1973 Overhaul Manual

1-8 AIR C O N D IT IO N IN G COMPRESSOR

Superheat Switch

The superheat switch is used on passenger cars and "G "
model trucks. If it becomes necessary to replace the
superheat switch, located in the rear head casting, the
switch assembly should be removed only after purging
the system. After the switch has been replaced and a new
"O " ring seal installed, the system should be evacuated
and recharged.

Rear Head, Oil Pump and Valve Assemblies

Removal
1. Remove the compressor from the vehicle, drain
compressor oil into a clean container, clean the
exterior of the compressor case and rear head
casting with a suitable solvent and mount the
compressor, rear head up, in Holding Fixture
J-9396 which should then be mounted securely in a
vise.
2. Remove the four nuts from the shell studs.
3. Remove the rear head. Examine the sealing surface
of the casting webs. If this surface is damaged by
nicks or scratches, the head should be replaced.
4. Examine the suction screen in the rear head for any
damage or contamination. Clean or replace the
screen as necessary.
5. Remove and examine the oil pump gears. If either
of the gears shows any wear or damage, replace
both gears.
NOTE: Keep the ends of the two oil pump
gears matched and replace the same end
toward the discharge plate upon reassembly.
6. Remove the rear head-to-shell "O" ring and
discard.
7. With two screw drivers, carefully pry up on the rear
discharge valve plate assembly (fig. 14). Check for
broken reeds or damaged seats and replace entire
assembly if such is found.
Excessive force during this opera­
CAUTION:
tion may loosen valve reed retainer rivets.
8. Carefully lift off the rear suction reed valve. Valve
must be replaced if any damage is evident.
Fig. 14 -Removing Rear Discharge Valve Plate
Fig. 1 5--P ro p e r O il Pum p G ear P o s itio n in g
Installation
1. Carefully replace the suction reed valve and the
rear discharge plate over the dowel pins and ports
in the cylinder assembly. Proper positioning of the
reed plate may be determined by lining up the
proper opening in the plate with the discharge
crossover tube opening.
2. Position the rear head casting to align with the
dowel pins. The two lower mounting pads will be in
alignment with the oil sump in the shell. Rotate the
cylinder assembly back and forth by hand, if
necessary, to permit this alignment. Remove the
rear head from this trial assembly.
3. Install the inner oil pump gear over the "D " flat on
the shaft and place the outer oil pump gear over the
inner gear. Position the outer gear as follows:
a. Observe the position of the oil sump in the shell.
b. Locate the approximate centerline of this sump.
c. Facing the centerline of the sump and viewing
from the sump side (bottom) of the compressor,
move the OUTER gear toward the right (side
having the oil drain fitting) until it is at
approximately 90 degrees (3 o'clock position)
from the centerline of the oil sump (fig. 15).
4. Coat the head-to-shell "O " ring with clean
refrigeration oil and generously lubricate the area
around the outer edge of the valve plate where the
"O" ring will be placed. Oil also the oil pump
OVERHAUL MANUAL