
HEATER AND AIR CONDITIONING 1A-21
"De-Fog"
Position
In the event that the front windshield should require
removal of a fogging condition, the owner at his option
may direct air to the windshield. The "De-Fog" position
directs part of the air to the windshield while retaining a
certain amount through the floor outlets. The temper-
ature of the air remains the same as it was prior to the
control being placed in the "De-Fog" position. Five
blower speeds are available. The temperature of the air
and the blower speed are selected by the automatic
controls and are dependent upon the in-car temperature.
"De-Ice" Position
The "De-Ice" position provides full heat with "Hi"
blower directing the entire airflow to the windshield to
melt ice. The automatic controls are completely defeated
and as a result, full heat with "Hi" blower are the only
conditions that can be received. The system will turn on
immediately in this position even though the engine
coolant might be cold.
General Information
Three start up conditions can be achieved with
Comfortron.
Weather
Cold
Method of Starting System
System starts as soon as engine coolant is
hot.
Hot System starts immediately when AC is
required.
Any System starts immediately in "De-Ice"
position.
UNIVERSAL SYSTEM
A self-contained unit, the dealer installed Universal
System operates on recirculated air only and entirely
independent of the vehicle heater. Recirculated inside air
is drawn into the unit, passed through the evaporator core
and into the car through the adjustable outlets in the
evaporator case. The entire unit mounts compactly
beneath the dash. Temperature control is by means of a
thermostatic switch.
The compressor used with the Universal System is
identical to that used for the Four-Season system except
for displacement. Underhood components are similar in
placement to the Four-Season system.
Controls
Universal system controls are the AIR knob controlling
the three speed blower motor switch and the TEMP knob
which controls the setting of the thermostatic switchi
Switch adjustment is covered elsewhere in this section.
When operating this system the Heater must be fully off.
CHEVY II ALL-WEATHER SYSTEM
The Chevy n All-Weather Air Conditioning System,
Figure 33, operates in conjunction with the heater to
provide a complete air conditioning system operating on
either outside air, recirculated air or a combination of
both. The cooling unit attaches to the heater distributor
and utilizes the heater blower. Several controls allow
full use of either the heating or cooling features of the
system. During marginal weather, it is possible to pro-
vide heated air at floor level and cooled air at breath
level.
A schematic view of the air conditioning underdash
components is provided in Figure 34 to aid in under-
standing airflow and control operation.
The evaporator assembly, located in the passenger
compartment attached directly to the heater distributor,
contains the evaporator core, expansion valve, thermo-
static switch and the air conditioning "ON" knob. The
thermostatic switch, utilized as the cooling control, feels
the temperature of the cooled air leaving the evaporator
core and turns the compressor on and off in accordance
with cooling needs. Refrigerant lines connect the evap-
orator assembly to the other system components located
in the engine compartment.
The six cylinder air conditioning compressor, com-
pletely field serviceable, is bracket-mounted to the
engine and is belt driven from the crankshaft pulley. A
muffler assembly, designed to eliminate compressor
pulsations is an integral part of the compressor con-
nector block. The condenser is mounted on the radiator
support just ahead of the engine radiator. The receiver-
dehydrator, with its sight glass, is located on the right
fender skirt.
Controls
Control of the air conditioning system is achieved
through the use of the heater control on the instrument
panel as well as the two knobs located on the air condi-
tioning unit itself (fig. 35).
Air Conditioning "ON" Knob
Labeled "Pull for Air Cond.", this knob diverts air-
flow from the floor distributor and through the air condi-
tioning unit. Initial movement of this knob also actuates a
switch, located at the damper door, which energizes the
compressor clutch thus putting the system into operation
and under the control of the thermostatic switch.
Temp-Cool Knob
This knob controls the thermostatic switch. Turn the
knob clockwise for more cooling, counter-clockwise for
less cooling.
Air Lever
This lever actuates the damper within the assembly
which chooses between recirculated air or outside air.
Fig.
31-Universal Air Conditioning Unit
CHEVROLET CHASSIS SERVICE MANUAL

HEATER AND AIR CONDITIONING 1A-26
clockwise for medium and high blower speed, as
desired. Low blower speed is automatic during
cooling operations.
4.
"Def-Pull". This knob should be pushed fully in.
Additional Cooling Hints
1.
The center barrel outlet in the dash may be rotated
to deflect air as desired or used to act as a shut off
door.
2.
The right and left ball outlets may be rotated to
deflect air in the direction desired. Each outlet has
a shut off valve operated by a knob approximately
4 in. inboard. When the knob is horizontal, the valve
is open.
3.
There are two (2) additional outlets in the bottom of
the ducts approximately 6" inboard from the valve
knobs. A rotating cover will open these outlets to
provide cool air for the feet if desired.
4.
When first entering a very warm car, open the
windows for a few minutes until the interior of the
car has cooled off.
Heating
1.
"Air Pull-Fan". Pull this knob fully out. Rotate
the knob clockwise for low, medium or high blower
speed as desired. If just a small amount of heat is
desired, leave the fan on low or medium speed and
regulate the temperature with the "Cool In-Hot Pull"
knob.
2.
"Air Cond-Pull". This knob should normally be
pushed fully in. However, during cool, damp days
it is possible, by pulling this knob fully out, to de-
humidify the air by passing it through the evaporator
core before reheating to the desired outlet
temperature.
3.
"Cool In-Hot Pull". Pull this knob out as far as
necessary to provide the temperature desired.
4.
"Def-Pull". Pull this knob all the way out for
maximum defrosting or de-icing. When the knob is
partly out, a portion of the hot air is used for de-
frosting and the balance is discharged through the
heater outlet.
GENERAL INFORMATION
In any vocation or trade, there are established proce-
dures and practices that have been developed after many
years of experience. In addition, occupational hazards
may be present that require the observation of certain
precautions or use of special tools and equipment. Ob-
serving the procedures, practices and precautions of
servicing refrigeration equipment will greatly reduce the
possibilities of damage to the customers' equipment as
well as virtually eliminate the element of hazard to the
serviceman.
PRECAUTIONS IN HANDLING REFRIGERANT-12
Refrigerant-12 is transparent and colorless in both the
gaseous and liquid state. It has a boiling point of 21.7^
below zero and, therefore, at all normal temperatures
and pressures it will be a vapor. The vapor is heavier
than air and is noninflammable, nonexplosive, non-
poisonous (except when in contact with an open flame)
and noncorrosive (except when in contact with water).
The following precautions in handling R-12 should be
observed at all times.
• All refrigerant drums are shipped with a heavy metal
screw cap. The purpose of the cap is to protect the
valve and safety plug from damage. It is good .prac-
tice to replace the cap after each use of the drum.
• If it is ever necessary to transport or carry a drum
or can of refrigerant in a car, keep it in the luggage
compartment. Refrigerant should not be exposed to
the radiant heat from the sun for the resulting in-
crease in pressure may cause the safety plug to
release or the drum or can to burst..
• Drums or disposable cans should never be subjected
to high temperature when adding refrigerant to the
system. In most instances, heating the drum or can
is required to raise the pressure in the container
higher than the pressure in the system during the
operation. It would be unwise to place the drum on a
gas stove, radiator or use a blow torch while pre-
paring for the charging operation, for a serious ac-
cident can result. Don't depend on the safety
plug - many drums have burst when the safety plug
failed.' Remember, high pressure means that great
forces are being exerted against the walls of the
container. A bucket of warm water, not over 125°F,
or warm wet rags around the container is all the heat
that is required.
• Do not weld or steam clean on or near the system.
Welding or steam cleaning can result in a dangerous
pressure buildup in the system.
• When filling a small drum from a large one, never
fill the drum completely. Space should always be
allowed above the liquid for expansion. If the drum
were completely full and the temperature was in-
creased, hydraulic pressure with its tremendous
force would result.
• Discharging large quantities of R-12 into a room can
usually be done safely as the vapor would produce
no ill effects, however, in the event of an accidental
rapid discharge of the system it is recommended
that inhalation of large quantities of R-12 be avoided.
This caution is especially important if the area con-
tains a flame producing device such as a gas heater.
While R-12 normally is nonpoisonous, heavy con-
centrations.. of it in contact with a live flame will
produce a toxic gas. The same gas will also attack
all bright metal surfaces.
• Protection of the eyes is of vital importance! When
working around a refrigerating system, an accident
may cause liquid refrigerant to hit the face. If the
eyes are protected with goggles or glasses, no
serious damage can result. Just remember, any
R-12 liquid that you can touch or that touches you is
at least 21.7"F. below zero. The eyeballs can't take
much of this temperature. If R-12 liquid should
strike the eyeballs, here is what to do:
1.
Keep calm.
2.
Do not rub the eyes! Splash the affected area with
quantities of cold water to gradually get the tem-
perature above the freezing point. The use of min-
eral, cod liver or an antiseptic oil is important in
CHEVROLET CHASSIS SERVICE MANUAL

HEATER AND AIR CONDITIONING 1A-47
are certain procedures, practices and precautions that
should be followed to prevent costly repairs, personal
injury or damage to equipment. For this reason it is
strongly recommended that the preceding information in
this section be studied thoroughly before attempting to
service the sytem.
Great emphasis must be placed upon keeping the sys-
tem clean. Use plugs or caps to close system components
and hoses when they are opened to the atmosphere. Keep
your work area clean.
In removing and replacing any part which requires
unsealing the refrigerant circuit the following operations,
which are described in this section, must be performed
in the sequence shown.
1.
Purge the system by releasing the refrigerant to the
atmosphere.
2.
Remove and replace the defective part.
3.
Evacuate and charge the system with R-12.
CAUTION: Always wear protective goggles
when working on refrigeration systems. Goggles
J-5453 are included in the set of air conditioning
special tools. Also, beware of the danger of
carbon monoxide fumes by avoiding running the
engine in closed or improperly ventilated
garages.
FOREIGN MATERIAL IN THE SYSTEM
Whenever foreign material is found in the system,
it must be removed before restoring the system to
operation.
In the case of compressor mechanical failure, perform
the following operations:
1.
Remove the compressor.
2.
Remove the receiver-dehydrator and discard me
unit.
3.
Flush the condenser to remove foreign material
which has been pumped into it.
4.
Disconnect the line from the receiver-dehydrator
at the inlet connection of the expansion valve. Inspect
the inlet screen for the presence of metal chips
or other foreign material. If the screen is plugged,
replace it. Reconnect the line to the expansion
valve.
5. Install a new receiver dehydrator.
6. Install the replacement compressor.
7. Add the necessary quantity of oil to the system (one
fluid ounce because of receiver-dehydrator replace-
ment plus the quantity needed for the replacement
compressor—see Checking Compressor Oil Charge
under Checking Oil.
8. Evacuate and charge the system.
9. Check system performance.
CONDENSER
Chevrolet
Replacement
1.
Remove the hood catch and hood catch - grille
support.
2.
With the system purged of refrigerant, disconnect
the inlet and outlet hose clamp connections and the
condenser to radiator support attaching screws.
3.
Remove the condenser from the vehicle.
NOTE:
If it is to be reused, cap or tape the
receiver-dehydrator inlet and outlet connections
at once.
4.
Install new condenser, position the assembly and
install the radiator support to condenser attaching
screws and replace all line connections.
5. Replace the hood catch and grille support and its
attaching bolts.
6. Replace the hood catch.
7. Evacuate, charge and check the system. Add one
fluid oz. refrigerant oil after installing a new
condenser.
Chevelle and Camaro
Replacement
1.
Remove the hood lock catch support and catch.
2.
With the system purged of refrigerant, disconnect
the inlet and outlet hose clamp connections and the
condenser to radiator support attaching screws.
3.
Remove the condenser from the vehicle.
NOTE:
Cap or tape the inlet and outlet con-
nections at once.
4.
Install new condenser, position the assembly and in-
stall the radiator support to condenser attaching
screws and replace all line connections.
5. Evacuate, charge and check the system. Add one
fluid oz. refrigerant oil after installing a new
condenser.
Chevy II
Replacement
1.
Purge the refrigerant from the system.
Fig.
59—Condenser Mounting (Chevrolet and Chevelle)
CHEVROLET CHASSIS SERVICE MANUAL

HEATER AND AIR CONDITIONING 1A-48
Fig.
60-Condenser Mounting (Chevy II)
2.
Remove the bumper, bumper filler panel, grille,
grille support, hood lock catch support and catch as
described in Section 11, "Chassis Sheet Metal".
3.
Disconnect connectors at condenser inlet and outlet
tubes and remove screws attaching refrigerant line
holding clips to the condenser baffle.
4.
Remove bolts attaching condenser through radiator
' support and slide condenser to the left and out of
vehicle.
5. Reverse these steps to reinstall new condenser.
6. Evacuate and charge the system. Add one fluid oz.
of refrigerant oil after installing a new condenser.
Corvette
Replacement (Production Engine)
1.
Remove the hood from the car, first scribing the
hinge attachment location.
2.
Purge the system of refrigerant.
Fig.
61—Condenser Mounting (Cdrnaro)
Fig.
62—Condenser Mounting (Corvette)
3.
Disconnect the inlet line connection at the condenser
inlet and the outlet line at the receiver-dehydrator.
Cap the receiver-dehydrator immediately.
4.
Remove the screws attaching the condenser to the
radiator support and carefully lift the unit from the
car.
5. Remove the receiver-dehydrator from the old con-
denser and install it, using a new "O" ring, on the
new condenser.
6. Set new condenser in place on the radiator support
and install the attaching screws, torquing them to
20 lbs. ft.
7. Make the inlet and outlet connections, using new
"O"
rings, and torque 13 lbs. ft.
8. Evacuate, charge and check the system. Add one
fluid oz. of refrigerant oil after installing a new
condenser.
Replacement (Optional Engine)
Replacement procedure remains much the same for the
installation supplied with the optional engine except for
the location of the receiver-dehydrator. Follow the steps
given above except that the outlet line must be removed
at the receiver outlet. (See Figure 64.)
RECEIVER-DEHYDRATOR
The receiver-dehydrator should be replaced if it has
been damaged through an accident or if it leaks or be-
comes restricted or clogged. Do not attempt to repair
the receiver-dehydrator.
The receiver-dehydrator is merely a moisture collect-
ing device and a refrigerant storage area and is the least
likely component of the system to cause a malfunction.
If at any time when examining the compressor oil,
moisture is found or there is an indication of moisture
at the expansion valve needle, the receiver-dehydrator
should be replaced as follows (fig. 63):
NOTE:
If the receiver-dehydrator is to be re-
used, cap the inlet and outlet connections
immediately. When installing a receiver-
dehydrator, do not uncap the connections until
CHEVROLET CHASSIS SERVICE MANUAL

HEATER AND AIR CONDITIONING 1A-49
CHEVROLET
CHEVELLE
CHEVY II
CAMARO
the last possible moment. Be certain that the
direction of flow is correct before connecting
the pipes.
Chevrolet, Chevelle, Chevy II, and Camaro
Replacement
1.
Remove the receiver inlet and outlet connections and
the two receiver to fender skirt attaching screws.
2.
Carefully remove the receiver-dehydrator from the
vehicle.
3.
Replace the new receiver~dehydrator assembly in
the vehicle and install all attaching screws and re-
frigerant lines.
4.
Add one fluid oz. refrigerant oil, evacuate and charge
the system.
Corvette
Replacement
1.
Purge the system of refrigerant.
2.
Disconnect the "O" ring inlet
hose clamp outlet connection
openings.
3.
Remove the receiver-dehydrator to radiator support
bracket screws (production engine) or receiver-
dehydrator to condenser bracket screws (optional
engine) and remove the unit from the car.
4.
Install the new receiver-dehydrator applying 30 in.
lbs.
torque to the attaching screws.
connection and the
and tape the hose
NOTE:
Do not uncap the new receiver-
dehydrator until the last instant before
installation.
5.
2.
3.
Fig.
63—
Receiver-Dehydrator Mounting (Chevrolet,
Chevelle/ Chevy II, Camaro)
Connect the high pressure lines at the inlet (use a
new "O" ring and torque connection to 13 ft. lbs.)
and outlet (torque screw to 25 in. lbs.).
6. Add one fluid oz. refrigerant oil, evacuate, charge
and check the system.
Sight Glass Replacement-All Vehicles
If damage to the sight glass should occur, a new sight
glass kit should be installed. The kit contains the sight
glass,
seal and retainer. (See Figure 65.)
1.
Purge system.
Remove the sight glass retainer nut using a screw
driver and remove old glass and seal.
Install the new glass and seal and retainer nut, being
careful not to turn the nut past the face of the hous-
ing. To do so may damage the "O" ring seal.
4.
Evacuate and recharge the system.
EVAPORATOR
Chevrolet and Camaro Four-Season System
The evaporator and blower case assembly is designed
so that the core may be removed without the need for
removing the entire unit from the vehicle. Instead,
only the side cover must be removed.
Removal and Installation of Entire Assembly
1.
Remove the inlet line at the expansion valve and the
suction throttling valve outlet connection.
2.
Remove the electrical connector from the blower
motor.
CHEVROLET CHASSIS SERVICE MANUAL

HEATER AND AIR CONDITIONING 1A-56
BLACK & RED
IGNITION—-y^****
SWITCH -"A
/
BLOWER LEAD—^^^
RESISTOR—-" \^<
ASM.
f'
i
'fu^^^^A^^^^^r"G^OUH£>
WIRE
^^
k4
^EVAPORATOR HARNESS
' EVAPORATOR & BLOWER ASM.
Fig.
73—Underdash Wiring—Universal System (Typical)
evaporator outlet pipes. Locate the bracket about
1/2" from the dash panel.
12.
Replace the inlet and outlet hoses and hose clamp
connections.
13.
Evacuate and charge the system. Add three fluid oz.
refrigerent oil after installing a new core.
14.
Check system performance.
Corvette
Replacement (Fig. 78)
1.
Purge the system of refrigerant.
2.
Drain the engine radiator. Then remove the radiator
supply tank from its brackets, the heater water
valve and vacuum line from the firewall, and the
heater hoses from the core pipes. Carefully fold the
hoses,
valve and tank away from the evaporator
case.
3.
Remove the right hand hood lock support.
SCREW DRIVER
(NARROW BLADE) T£
GROOVE
A. Insert screw driver in
tang toward terminal
B. Pry tang back out to
when reinstalled into
RMINAL
\ CONNECTOR
TANG
groove & press
to release.
insure locking
connector.
Fig.
74—Terminal Removal—Universal System
4.
Disconnect the expansion valve equalizer line con-
nection and the evaporator oil bleed line from the
POA.
5.
Disconnect the evaporator outlet to POA inlet
connector.
6. Remove the POA bracket to evaporator case attach-
ing bolts. Then carefully move the valve and its
outlet hose away from the evaporator case.
Fig.
75-Cable Removal-All Weather
CHEVROLET CHASSIS SERVICE MANUAL

HEATER AND AIR CONDITIONING 1A-57
EVAPORATOR PIPES
DISTRIBUTOR RELAY GRD.
ASSEMBLY & WASHER
EVAPORATOR ASM.
BLOWER
SHROUD
(RACKET
(PART OF
BLOWER)
Fig.
76—Evaporator Removal—All Weather
7. Disconnect the thermostatic expansion valve to evap-
orator inlet connector, remove the power element
bulb from the evaporator outlet line and carefully
move .the valve and its inlet hose away from the
evaporator case.
8. Remove the electrical connectors from the relay
and resistor terminals.
9. Remove the screws attaching the evaporator case
cover to the case. See Fig. 79. The core is bracket
mounted to the cover and the entire core and cover
assembly may now be removed from the vehicle.
10.
Remove the two cover to core bracket screws and
separate the core from the cover.
11.
Install the new core to the cover being sure that the
grommets are properly installed around the inlet
and outlet lines.
12.
Reinstall the core and cover assembly into the evap-
orator case and replace the attaching screws.
13.
Reinstall the STV and expansion valves, the equal-
izer line connection and the evaporator oil bleed line
from the STV.
NOTE:
Use all new «O" rings.
14.
Reinstall the radiator supply tank, water valve and
vacuum line, and replace the heater hoses onto the
core pipes being sure not to switch the hoses. Then
refill the radiator.
15.
Add three fluid oz. refrigerant oil after installing a
new core, evacuate and charge the system.
EXPANSION VALVE
The thermostatic expansion valve is factory adjusted
and pre-set and cannot be adjusted after installation. A
malfunctioning valve must be replaced. However, before
proceeding, check all other possible causes of the trouble.
Make certain that the power element bulb is properly
CHEVROLET CHASSIS SERVICE MANUAL

HEATER AND AIR CONDITIONING 1A-62
2.
Insert the evaporator assembly into the outlet case
half and mount the evaporator, thermostatic switch,
and cable to the case.
3.
Install the face plate to the case and install control
retaining nuts and knobs.
4.
Assemble the case halves and mount the evaporator
pipe clamp.
5. Install the evaporator assembly as previously
described under EVAPORATOR.
BLOWER ASSEMBLY
Four-Season System
Chevrolet and Camaro
Removal
1.
Disconnect battery ground cable.
2.
Remove the right front fender and skirt assembly.
3.
Disconnect the motor wire at the flange connector.
4.
Disconnect the rubber air cooling tube from the
motor.
5. Remove the motor to case attaching screws and re-
move the blower assembly. If the sealer acts as an
adhesive, pry the assembly carefully away from the
6. Remove the blower from the motor shaft.
Fig.
86—Blower Assembly—Four-Season (Chevrolet,
Chevelle, Camaro)
Installation
1.
Mount the blower to the motor shaft with the open end
of the blower away from the motor.
2.
Mount the assembly to the case with the attaching
screws.
3.
Connect the rubber tube and blower wire to the
motor.
4.
Replace the right front fender and skirt assembly.
5. Connect battery ground cable.
Chevelle
The blower assembly (fig. 86) is mounted to the dash
panel and contains the outside air-recirculated air
diverter door, the heating-cooling diverter door, the air
conditioning relay and resistor, the compressor actuating
switch, and the blower motor.
Replacement
1.
Disconnect the blower motor "hot" wire at the con-
nector and the ground lead on the Chevrolet.
2.
Detach the rubber cooling tube from the blower as-
sembly and remove the five bolts attaching the
blower motor to the blower assembly.
3.
Remove the motor and fan, disassemble fan from
motor and install on a new motor. If, because of
engine accessories, hoses restrict lifting the blower
assembly from the engine compartment, remove
blower from motor and lift units out separately.
Assemble replacement units under the restricting
hoses.
4.
Reinstall motor and fan into blower assembly. Re-
place cooling tube, ground wire and connect hot wire
to connector.
5. Check blower operations.
Corvette
Replacement
1.
Remove the radiator overflow tank and brackets and
pull the tank out of the way as far as the length of the
heater hose will permit.
2.
Disconnect the electrical connector and the rubber
air inlet tube from the blower motor.
3.
Remove the five blower flange to case attaching
screws and carefully remove the blower motor and
drum assembly.
4.
Remove the blower drum assembly and reinstall on
a new blower motor.
5. Replace the blower motor and drum assembly in the
case and reinstall all screws, hoses and electrical
connections.
All-Weather System
Chevy II
Removal
Under the Hood
1.
Purge the refrigerant from the system.
2.
Drain the radiator.
3.
Remove the refrigerant hoses at the evaporator
pipes.
4.
Remove the evaporator pipe clamp and grommet.
5. Remove three nuts from the blower case studs which
pass through the firewall.
6. Remove heater hoses from core tubes.
CHEVROLET CHASSIS SERVICE MANUAL