Chevrolet 10 Series 1968, Service Manual

Page: 42 / 713

HEATER AND AIR CONDITIONING 1A-11
AIR CONDITIONING
INDEX
Page
General D e s c r ip t io n ........................................................ . 1A-11
General I n fo r m a t io n ............................................................. 1A-13
Precautions in Handling R efrigeran t— 1 2 .......................1A-13
Precautions in Handling R efrigeran t L in e s ................... 1A-14
Maintaining Chemical Stability In the
R efrigeratio n S y s te m .......................................................1A-14
J-8393 Charging S t a t io n ................................................... 1A-15
Gauge S e t ............................................................................. 1A-15
Vacuum P u m p .......................................................................1A-15
Leak Testing The S y s t e m ................................................ 1A-16
A vailab ility of R efrigeran t— 1 2 .......................................1A-17
C om pressor Oil ....................................................... 1A-17
Com pressor Serial N u m b e r ............................................. 1A-17
Inspection and P erio d ic S e r v ic e ..........................................1A-17
P re -D e liv e ry In s p e c tio n ................................................... 1A-17
6000 M ile In s p e c tio n .......................................................... 1A-18
P erio d ic S e r v i c e ................................................................ 1A-18
Installing Charging Station to Check System Operation . 1A-18
Perform ance T e s t ............................................................. 1A-18
Perform ance D a t a ............................................................. 1A-18
Evaporator Control Valve ( P O A ) ................................... 1A-18
Expansion V a l v e ................................................................ 1A-19
Engine Idle Compensator
................................................ 1A-19
Evacuating and Charging P r o c e d u r e s ................................ 1A-20
A ir Conditioning System C a p a c ity ................................... 1A-20
Purging the System
.......................................................... 1A-20
Evacuating and Charging the S y s t e m ............................. 1A-20
Checking O i l .......................................................................1A-20
Page
Adding Oil to the System .................................................1A-22
Component Replacement and Minor R e p a i r s ................... 1A-22
Preparin g System for Replacement of
Component P a r t s ............................................................. 1A-22
F oreign M aterial in the S ystem ....................................... 1A-22
R efrigeran t Line C o n n e c tio n s ..........................................1A-23
Repair of R efrigerant L e a k s ............................. ............... 1A-23
R efrigeran t Hose Failure .................................................1A-23
Control Assem bly
.............................................................1A-24
Condenser ......................................................................... 1A-24
R ece iver - D eh yd rator.......................................................1A-25
Sight Glass Replacement
................................................ 1A-26
Expansion V a l v e ................................................................ 1A-26
P .O .A . V a l v e .......................................................................1A-26
Blower A s s e m b ly ................................................................ 1A-27
Evaporator C o r e ................................................................ 1A-27
Blower and Evaporator C a s e ..........................................1A-27
Heater C a s e ..........................................................................1A-28
Heater C o r e ..........................................................................1A-29
Blower R esistor U n it..........................................................1A-29
M uffler and Connector B l o c k ..........................................1A-29
Kick Panel A ir V a l v e ...................................................... 1A-29
Plenum A ir Valve
..........................................................1A-30
C o m p re s so r......................................................................... 1A-31
W iring D ia g ra m ...................................................................... 1A-34
Special Tools
.......................................................................1A-35
Specifications . .......................................................................
GENERAL DESCRIPTION
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. A ll cooling system components are connected
by means of flexible refrigerant lines.
Both the heating and cooling functions are performed
by this system. A ir entering the vehicle must pass
either through the cooling unit (evaporator) or through
the heating unit, or through both. The system is thus
referred to as a parallel system.
The evaporator provides maximum cooling of the air
passing through the core when the air conditioning sys­
tem is calling for cooling. The control valve acts in the
system only to control the evaporator pressure so that
minimum possible temperature is achieved without core
Fig . 22—Four-Season System Controls
freeze-up. The valve is preset, has no manual control,
is automatically altitude compensated, and non-repairable.
The heater core will be hot at all times since no water
valve is present in the system.
System operation is as follows (See Figure 23): Air,
either outside air or recirculated air enters the system
and is forced through the system by the blower.
The air passes by the temperature door and is directed
through the heating or cooling cores, or split to flow
through both. After flowing through the core or cores,
the air passes the outlets door which directs it to the
dash or floor outlets or both. Air directed to the dash
outlets is finally controlled by the position of the air
outlets. A ir directed to the floor outlets passes the
defroster door which directs the air out the floor outlets,
the defroster outlets, or both.
Linkage is so designed that when the system controls
are calling for heat, air will enter the vehicle through the
floor distributor duct, and when the system controls call
for cooling, air will enter through the three dash outlets.
The side dash outlets may be rotated to provide either
soft, diffused airflow or spot cooling. Rotate half way to
shut off airflow. The barrel type outlet in the center of
the dash will direct air up or down or, if desired, shut it
off.
CONTROLS
Full control of the Four-Season System is obtained
through the use of a single control panel (fig. 22). The
control levers make use of bowden cables to activate the
various doors and switches necessary for system opera­
tion. Control adjustment is a matter of properly setting
these bowden cables. The following paragraphs explain
each control.
CHEVROLET TRUCK SERVICE MANUAL