GMC 1982 Light Duty Truck Service Manual page 115

2. "Evacuate and Charge the Refrigerant System" according to
the directions in Section 1B1.
R-4 C O M P R E S S O R LEAK T E S T IN G (E X T E R N A L
A N D IN T E R N A L )
Bench-Check Procedure
1. Install Test Plate J 9625 on Rear Head of compressor.
2. Attach center hose of Manifold Gage Set on Charging Station
to a refrigerant drum standing in an upright position and
open valve on drum.
3. Connect Charging Station high and low pressure lines to
corresponding fittings on Test Plate J 9625, using J 5420
Gage Adapters if hoses are not equipped with valve
depressors.
• Suction port (low-side) of compressor has large internal
opening. Discharge port (hi-side) has smaller internal
opening into compressor.
4. Open low pressure control, high pressure control and
refrigerant control on Charging Station to allow refrigerant
vapor to flow into compressor.
5. Using a Leak Detector, check for leaks at Pressure Relief
Valve, compressor shell to cylinder, compressor front head
seal, and compressor Shaft Seal. After checking, shut off low
pressure control and high pressure control on Charging
Station.
6. If an external leak is present, perform the necessary corrective
measures and recheck for leaks to make certain the leak has
been corrected.
7. Loosen the Manifold Gage hose connections to the Gage
Adapters J 5420 connected to the low and high sides and
allow the vapor pressure to release from the compressor.
8. Disconnect both Gage Adapters J 5420 from the Test Plate
J 9625.
9. Rotate the complete compressor assembly (not the crankshaft
or drive plate hub) slowly several turns to distribute oil to
all cylinder and piston areas.
10. Install a shaft nut on the compressor crankshaft if the drive
plate and clutch assembly are not installed.
AIR C O N D ITIO N IN G COM PRESSOR OVERHAUL 1C 1-17
11. Using a box-end wrench or socket and handle, rotate the
compressor crankshaft or clutch drive plate on the crankshaft
several turns to ensure piston assembly to cylinder wall
lubrication.
12. Connect the Charging Station high pressure line or a high
pressure gage and Gage Adapter J 5420 to the Test Plate J
9625 high side connector.
13. Attach an Adapter J 5420 to the suction or low pressure port
of the Test Plate J 9625 to open the schrader-type valve.
Oil will drain out of the compressor suction port adapter if
the compressor is positioned with the suction port downward.
14. Attach the compressor to the Holding Fixture J 25008-1
using metric mounting screws. Clamp the compressor
Holding Fixture in a vise so that the compressor can be
manually turned with a wrench.
15. Using a wrench, rotate the compressor crankshaft or drive
plate hub ten (10) complete revolutions at a speed of
approximately one-revolution per second.
Turning the compressor at less than one-revolution per
second can result in a lower pump-up pressure and disqualify
a good pumping compressor.
16. Observe the reading on HIGH pressure gage at the
completion of the tenth (10th) revolution of the compressor.
The pressure reading for a good pumping compressor should
be 344.75 kPa (50 P.S.I.) or above. A pressure reading of less
than 310.275 kPa (45 p.s.i.) would indicate one or more
suction and/or discharge valves leaking, an internal leak, or
an inoperative valve and the compressor should be
disassembled and checked for cause of leak. Repair as needed,
reassemble and repeat the pump-up test. Externally leak test.
17. When the pressure pump-up test is completed, release the air
pressure from the HIGH side and remove the Gage Adapters
J 5420 and Test Plate J 9625.
18. On the R-4 compressor, tilt the compressor so that the
compressor suction and discharge ports are down. Drain the
oil from the compressor.
19. Allow the compressor to drain for 10 minutes, then charge
with the proper amount of oil. The oil may be poured into
the suction port.
If further assembly or processing is required, a shipping plate
or Test Plate J 9625 should be installed to keep out air, dirt
and moisture until the compressor is installed.