GMC 1986 P-Truck Service Manual page 78

Clutch slipping.
— I Belt slipping!
Com pressor engaged
but not operational.
High torque
com pressor (seized).
Blow oil seal cavity
Com pressor throws oil. with air hose and leak
test.
Noisy only when
clutch is engaged.
Noisy when clutch
is not engaged.
NOTE: A/C system noise is to be evaluated in the vehicle with doors and windows closed and low blower on.
COMPRESSOR DIAGNOSIS
Check for proper air gap.
Correct if necessary
0.56 - 1.45 mm (0.022 - 0.057 in.
Check and correct belt tension.
Refrigeration charge is depleted.
L- System has some refrigerant.
Leaks refrigerant.
J- Does not leak refrigerant.
Check for refrigerant lines touching
metal parts. Isolate and re-evaluate
noise.
Remove compressor belt to
determine if noise still persits.
If previous step does not
correct clutch slippage,
repair compressor.
Add one pound refrigerant.
Leak test complete Repair compressor.
system before removing
Operate and leak
compressor. test system.
Repair compressor.
Wipe off oil - OK
Repair compressor
Check and adjust
belt tension. if noise is
objectionable.
Check for interference If interference exists,
between coil housing
repair compressor.
and pulley hub.
F-00166