54 SECTION 50 - CAB HEATING AND AIR CONDITIONING
FAULT FINDING
During diagnosis follow the inspections procedures in the sequence shown until a default is found. Then per-
form the repair in the “Cause and Remedy” section. If this repair does not fully solve the problem, proceed to
the next inspection step.
PROBLEM CAUSE CORRECTION
Unusually high suction pres-
sure with unusually low dis-
charge pressure
Valve plate test Replace or repair:
Broken head or block gasket.
Broken or deformed reed valve.
Foreign substance under reed valve
or gasket.
Unusually low suction and dis-
charge pressure
Check for low refrigerant charge
Leak check compressor
Leak check and diagnose system
Replace or repair:
Shaft seal leak.
Cylinder head leak.
Gasket leak.
Oil filler plug leak.
Cracked cylinder block.
Front housing O-ring leak.
Intermittent or inoperative Check belt tension
Check clutch air gap
Check clutch volts, amps, coil lead
wire
Replace.
Adjust air gap.
Replace or repair:
Broken lead wire.
Clutch coil defect - Internal.
System ground (see system man-
ual).
Rough running Shaft turning smoothness test Compressor failure - Internal.
PROBLEM CAUSE CORRECTION
Clutch engaged Check compressor mounting compo-
nents
Check engine components
Check for intermittent or slipping
clutch
Check for proper refrigerant charge
Check clutch bearing
Oil level procedure
Shaft turning smoothness test
Remove valve plate and inspect
Replace or repair.
Replace or repair.
Adjust air gap - defective coil.
Recharge and recheck.
Replace rotor / Armature assembly.
Fill to proper level.
Compressor failure (Internal).
Replace or repair:
Broken discharge valve reed or
retainer.
Broken suction valve reed.
Broken gasket.
Clutch disengaged “chattering” Check air gap Replace or repair:
Adjust air gap.
Defective clutch pulley or front plate.
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