Air Conditioning; Four-Season System - Chevrolet 10 1971 Series Chassis Service Manual

General D e s c rip tio n ..................................................................................1A-7
Four-Season System ........................................................................... ..1A-7
Roof-Mounted System .........................................................................1A-9
GM Chevrolet S y s te m ......... ...................................... .. . . , .............. ..1A-10
General In fo rm a tio n ................................................................................ ..1A-12
Precautions in Handling Refrigerant-12........................................... ..1A-12
Precautions in Handling Refrigerant Line s.........................................1A-12
Maintaining Chemical Stability in the
Refrigeration S y s te m .........................................................................1A-13
J-8393 Charging Station .................................................................... ..1A-13
Gauge Set ................................................................................................1A-14
Vacuum P u m p ........................... ........... ........................... .................... ..1A-14
Leak Testing the S y ste m .......................................................................1A-15
Availability o f Refrigerant-1 2 ..............................................................1A-15
Compressor O i l .......................................................................................1A-16
Compressor Serial Number ................................................................ ..1A-16
Inspection and Periodic Service ..............................................................1A-16
Pre-Delivery In sp e ctio n ....................................................................... ..1A-16
6000 Mile Inspection........................................................................... ..1A-16
Periodic Service.......................................................................................1A-16
Installing Charging Station to Check System
O p e ra tio n ........................................................................................... ..1A-16
Performance Test ..................................................................................1A-16
Performance D a t a ................................................................................ ..1A-17
Evaporator Control Valve (P O A ).........................................................1A-18
Thermostatic S w itc h ........................................................................... ..1A-18
Expansion V a lv e .................................................................................. ..1A-19
Engine Idle C om pensator....................................................................1A-20
Evacuating and Charging Procedures .................................................. ..1A-20
Air Conditioning System Capacity .................................................. ..1A-20
Purging the S y s te m ................................................................................1A-20
Evacuating and Charging the S y ste m ................................................ ..1A-20
Refrigerant Quick-Check Procedure . . ..............................................1A-22
Checking O i l ......................................................................................... ..1A-22
Component Replacement and Minor R e p a irs .......................................1A-23
All System s........................................................................................... ..1A-23
Preparing System for Replacement o f
Component Parts........................................................................... ..1A-23
Foreign Material in the System ....................................................... ..1A-23
Refrigerant Line Connections......................................................... ..1A-23
Repair o f Refrigerant L e a k s ........................................................... ..1A-24
Refrigerant Hose Failure ................................................................ ..1A-24
Compressor .........................................................................................1A-25
Condenser ......................................................................................... ..1A-26

FOUR-SEASON SYSTEM

The Four-Season system uses an evaporator pressure
control known as the POA (Pressure Operated Absolute)
valve. The six-cylinder reciprocating compressor is
bracket-mounted to the engine and belt driven from the
crankshaft pulley. The condenser is mounted ahead of the
engine cooling radiator and the receiver-dehydrator is
mounted in the refrigerant line downstream of the con­
denser. All cooling system components are connected
by means of flexible refrigerant lines.
Both the heating and cooling functions are performed
by this system. Air entering the vehicle must pass

AIR CONDITIONING

INDEX
Page
Four-Season System ..............................................................................1A-27
Roof-Mounted System ....................................................................... ..1A-34
Compressor, Condenser, Receiver-Dehydrator
Control Switch and/or Front D u c t ................................................ ..1A-34
Intermediate Duct ..............................................................................1A-35
Thermostatic Switch, Blower M otor Relay
Expansion V alve ................................................................................ ..1A-36
Evaporator C o r e ................................................................................ ..1A-37
Muffler and Connector B lo c k ......................................................... ..1A-37
Anti-Dieseling R e la y ......................................................................... ..1A-37
GM Chevrolet S y s te m ......................................................................... .. 1A-38
Compressor, Condenser, Receiver-Dehydrator
Blower Resistor ................................................................................ ..1A-38
Evaporator Core, Expansion Valve, Blower Motor
Wiring D iagram s....................................................................................... ..1A-41
Special Tools ..............................................................................................1A-44
GENERAL DESCRIPTION
either through the cooling unit (evaporator) or through
the heating unit, or through both.
referred to as a parallel system.
HEATER AND AIR CONDITIONING 1A-7
Receiver-Dehydrator ....................................................................... ..1A-26
Sight Glass Replacement ................................................................ ..1A-26
Blower A ss e m b ly .............................................................................. ..1A-27
Evaporator C o r e ................................................................................ ..1A-27
Blower and Evaporator Case..............................................................1A-28
Heater Case ....................................................................................... ..1A-28
Heater Core ....................................................................................... ..1A-28
Water Valve ....................................................................................... ..1A-29
Expansion V alve ................................................................................ ..1A-29
Muffler, Connector Block and Hose A sse m bly ........................... ..1A-29
POA V a lv e ......................................................................................... ..1A-30
Control Assem bly.............................................................................. ..1A-31
Blower Motor S w itc h ....................................................................... ..1A-31
Blower Motor R e la y ......................................................................... ..1A-32
Anti-Dieseling R e la y ......................................................................... ..1A-32
Compressor Clutch S w itc h .............................................................. ..1A-32
Blower Resistor Unit ....................................................................... ..1A-32
Kick Panel Air Valve ....................................................................... ..1A-33
Plenum Air V a lv e .............................................................................. ..1A-33
and/or Sight G la s s ......................................................................... ..1A-34
Rear D u c t ..............................................................................................1A-35
and/or Blower M otor Resistor.......................................................1A-35
Blower Motor Assemblies................................................................ .. 1A-35
and/or Sight G la s s ......................................................................... ..1A-38
Anti-Dieseling R e la y ......................................................................... ..1A-38
Blower and/or Thermostatic Switches ......................................... ..1A-38
and Wheels ..................................................................................... ..1A-39
Fig. 13— Four Season System Controls
Page
The system is thus
10-30 CHEVROLET TRUCK SERVICE MANUAL