Chevrolet Light Duty Truck 1973, Service Manual

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HEATER A N D AIR C O N D IT IO N IN G 1A-19
Receiver-Dehydrator.......................................................1A-76
Sight G lass........................................................................1A-76
Blower-Evaporator Assembly...................................... .1A-76
Blower Assembly............................................................ .1A-77
Expansion Valve, Evaporator Case or Core..........1A-77
Thermostatic and/or Blower Switches.....................1A-78
Resistor...............................................................................1A-78
Fuse.....................................................................................1A-78
Diagnosis..............................................................................1A-78
Refrigerant System.........................................................1A-78
Compressor Diagnosis....................................................1A-80
Insufficient Cooling........................................................ 1A-81
Electrical System Diagnosis........................................ .1A-83
Vacuum System Diagnosis.......................................... .1A-87
Special Tools.......................................................................1A-94
GENERAL DESCRIPTION
FOUR-SEASON SYSTEM (C-K MODELS)
Both the heating and cooling functions are performed by
this system. Air enterning the vehicle must pass through
the cooling unit (evaporator) and through (or around)
the heating unit, in that order, and the system is thus
referred to as a "reheat" system.
The evaporator provides maximum cooling of the air
passing through the core when the air conditioning
system is calling for cooling. A thermostatic switch,
located in the blower-evaporator case, acts to control
compressor operation by sensing the fin temperature of
the evaporator core.
System operation is as follows: Air, either outside air or
recirculated air, enters the system and is forced through
the system by the blower. As the air passes through the
evaporator core, it receives maximum cooling if the air
conditioning controls are calling for cooling. After
leaving the evaporator, the air enters the Heater and Air
Conditioner Selector Duct Assembly where, by means of
diverter doors, it is caused to pass through or to bypass
the heater core in the proportions necessary to provide
the desired outlet temperature. Conditioned air then
enters the vehicle through either the floor distributor
duct or the dash outlets. When, during cooling
operations, the air is cooled by the evaporator to below
comfort level, it is then warmed by the heater to the
desired temperature. During "heating only" operations,
the evaporator will not be in operation and ambient air
will be warmed to the desired level in the same manner.
The dash outlets are rectangular in design. The outlets
can be rotated horizontally or vertically to direct air as
desired. Under the left distributor duct is located a floor
cooler which can be rotated to provide cooling air or shut
off completely.
FLOOR MOUNTED SYSTEM (G MODELS)
This system (C62) performs the cooling functions only.
When heating (above ambient temperatures) is desired,
the standard equipment heater must be used. When air
conditioning is desired, be sure the heater is completely
shut off.
This self contained unit (fig. 22), operates on recirculated
inside air only. Recirculated air is drawn into the unit,
passes through the evaporator core (receiving maximum
cooling) and then directed into the vehicle through
adjustable outlets located in the ducts.
A thermostatic switch, located on the evaporator cover, is
used to control compressor operation by sensing air
temperature as it leaves the evaporator core.
OVERHEAD SYSTEMS (C-K-G MODELS)
These systems (C69 on C-K Models, C63 on G Models)
operate in conjunction with the Four-Season System (C-
K Models) or Floor Mounted System (G Models)-they
do not operate independently.
NOTE: Overhead system kits are available
for non-factory installation on C-K Models,
providing the vehicle is equipped with the
front system.
Like the floor-mounted system, these units are self
contained, operating on inside (recirculated) air only. Air
is drawn into the unit, passed through the evaporator
core and then directed into the passenger compartment
through adjustable outlets in the air distributor duct.
System control is through the thermostatic switch in the
front system. The only control on the overhead system is
a three speed blower switch.
MOTOR HOME CHASSIS SYSTEM
This system performs the cooling functions only. When
Fig. 22--C62 Interior Components (G Models)
LIGHT DUTY TRUCK SERVICE MANUAL