GMC 4000 Series Service Manual page 76

This sub-section contains service information on the following:
Subject
General Information
Operating Instructions
System Operation
On-Vehicle Service
Insufficient Cooling Diagnosis Chart
The optional air conditioning system used on
conventional cab models operates in conjunction
with the heating system to cool and dehumidify the
incoming air, the recirculated inside air, or a
mixture of both as required for optimum driver
comfort. Briefly, the air conditioning system is
comprised of the following basic system s:
CONDENSING SYSTEM
This system is composed of three major units
which are located behind the radiator shell sheet
metal assem bly. Units are described as follows:
1. The six-cylinder double-action piston-type
com pressor, which is belt-driven by the engine
crankshaft through an electromagnetic clutch-
pulley assem bly. The com pressor pumps refriger­
ant through the system as required and operates
when the com pressor clutch coil is energized. The
com pressor is equipped with an automatic high
A ir O u tle t
Deflector
DASH OUTLETS
G M C S E R V I C E M A N U A L
A il G&n&itiosiincj,
(CONVENTIONAL CAB MODELS)
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GENERAL INFORMATION
pressure relief valve to reduce excessive refrig­
erant pressure.
serviceable. The com pressor, which may be re ­
moved for repairs, is mounted towards front of
engine parallel to the engine crankshaft.
designed to change entering refrigerant vapor to a
liquid by the removal of heat. The condenser is
mounted in front of engine cooling radiator where
it receives a high volume of air from movement of
the vehicle and the engine fan.
mounted to right side of radiator shell, is designed
to store liquid refrigerant and to remove small
traces of moisture that may be in system after
purging and evacuating. A sight glass at the top of
this component is used to observe flow of liquid
refrigerant in system .
W INDSHIELD
OUTLETS
DISTRIBUTOR
M A N IFO LD
OUTLET D O O R
BLOWER
Figure 1 — System A ir-Flow
Page No.
70
72
79
96
The complete com pressor-clutch assembly is
2. Tne condenser is a fin and tube-type core
3. The receiver and dehydrator unit, usually
EVAPORATOR
CORE
RECIRCULATED
AIR
TEMPERATURE
SELECTOR D O O R
Sec. 1
Page 69
69
OUTSIDE
AIR
HEATER CORE