Chevrolet LIGHT DUTY TRUCK (SERIES 10-35) Service Manual page 72

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abnormal condition and will lead to evaporator freeze-up.
The problem is either loose clamps around the capillary tube
to the evaporator inlet pipe or a defective switch.
• If the compressor does not operate, thermostatic
switch is defective (provided that it has been established that
battery voltage is available at one switch terminal with the
A /C "on"). This, of course, results in no cooling. Replace
the switch.
• The thermostatic switch is pre-set and cannot be
adjusted. When trouble shooting the refrigerant system,
refer to "C.C.O.T. A /C System Diagnostic Procedures".
Engine Idle Com pensator
On V8 Engines, with factory installed air conditioning
systems, the compensator is located within the carburetor
and is accessible when the engine air cleaner is removed.
All compensators are factory set and non adjustable.
A malfunctioning unit should be replaced.
The following is a description of the type of symptom
each refrigerant component will evidence if a defect occurs:
COMPRESSOR
A compressor defect will appear in one of four ways:
Noise, seizure, leakage, or low discharge pressure.
Resonant compressor noises are not cause
NOTICE:
for alarm; however, irregular noise or rattles may
Fig. 1B -2 5 -C 6 0 System W irin g Diagram (G Models)
CONDENSER
or it may be restricted. A condenser restriction will result
in excessive compressor discharge pressure. If a partial
restriction is present, sometimes ice or frost will form
immediately after the restriction as the refrigerant expands
after passing through the restriction. If air flow through the
condenser or radiator is blocked, high discharge pressures
will result. During normal condenser operation, the outlet
pipe will be slightly cooler than the inlet pipe.
AIR CONDITIONING
indicate broken parts or excessive clearances due to
wear. To check seizure, de-energize the magnetic
clutch and check to see if drive plate can be rotated.
If rotation is impossible, compressor is seized (See
"False Compressor Seizure"). To check for a leak, refer
to leak testing in the service manual. Low discharge
pressure may be due to a faulty internal seal of the
compressor, or a restriction in the compressor.
Low discharge pressure may also be due to an
insufficient refrigerant charge or a restriction elsewhere
in the system. These possibilities should be checked
prior to servicing the compressor. If the compressor is
inoperative, but is not seized, check to see if current
is being supplied to the magnetic clutch coil terminals.
A condenser may be defective in two ways: it may leak,
IB -2 9
AIR CONDITIONING
RP.0.-C60
LIGH T T R U C K S ER V IC E M ANUAL