CHEVROLET CAMARO 1967 1.G Chassis Service Manual

HEATER AND AIR CONDITIONING 1A-18

HIGH BLOWER

i DELAY RELAY

AMBIENT-SUN

SENSOR AND

COMPRESSOR SWITCH

Fig. 29—Comfortron Engine Compartment Components

COMFORTRON SYSTEM

The Chevrolet Comfortron Air Conditioning System is

basically the same as the Chevrolet Four-Season system

but with the additional feature of completely automatic

control. See Figures 28, 29 and 30 for views of the

Comfortron system. To the customer, the most notice-

able difference between the two systems, will be in the

control panel. In place of the three-lever/one-switch

panel of the Four-Season system, the Comfortron has a

single control lever plus a temperature dial similar to

that found in a home thermostat. After the dial is set to

the desired temperature indication and the lever is moved

to place the system in operation, the Comfortron will

automatically control the heating and air conditioning

functions to maintain the selected interior temperature

regardless of changes in outside air temperatures.

Most Comfortron parts are located in the passenger

compartment, (fig. 28)

Jn-Car Sensor

The function of the in-car sensor is to determine the

temperature of the interior of the automobile. It is

located beneath the overhang of the instrument panel.

Feedback Potentiometer

The feedback potentiometer indicates to the amplifier

system the position of the temperature door.
Control Head

A thumb wheel is provided to select the desired in-car

temperature. A control lever performs the following

functions:

1.
Operates a switch that allows the customer to select

the type of blower program desired.

2.
Operates the control head vacuum switch except

when the TEMPERATURE lever is in the OFF

position, thus programming the vacuum system.

3.
Operates the defroster through the control head

vacuum switch. The defroster door is partially

opened in the "DE FOG" position, and fully open in

the "DE ICE" position.

A two transistor amplifier is located on the bottom

side of the control head. It receives information from

the sensors, and in turn operates the transducer.

Fig. 30—Comfortron Control

CHEVROLET CHASSIS SERVICE MANUAL

HEATER AND AIR CONDITIONING 1A-19

Transducer

The transducer will produce a vacuum output that is

completely adjustable by varying the input voltage which

is provided by the amplifier. An increase in the applied

voltage results in a reduced vacuum output.

Power Servo

The power servo receives a vacuum signal from the

transducer, and it is capable of assuming any position

that is called for by the sensors, amplifier, and trans-

ducer. The power servo performs the following functions:

1.
Positions the temperature mix door via the tern-

perature door link. The position of this door~"de-

termihes the portions of hot and cold air being

blended and discharged into the car.

2.
Operates the power servo vacuum valve which de-

termines the air flow paths for heating and air

conditioning.

3.
Contains a printed circuit board which controls the

blower speed. The power servo position determines

the blower speed, but the control lever switch can

override the blower program depending upon the

customer's preference.

4.
Contains the "Hi" blower delay thermistor and the

"master delay thermistor".

Outside Air Diaphragm

When there is no vacuum applied to the hose, the out-

side air door is closed under spring tension. With the

door closed, air is taken from the inside of the auto-

mobile and re-circulated. Applying vacuum to the dia-

phragm opens the door for outside air.

Mode Door Diaphragm

Located behind the duct work, the mode door diaphragm

directs the air flow out either the air conditioning outlets,

the heater floor outlet, or both the heater and air con-

ditioning outlets. This is a push-pull type diaphragm

actuated by vacuum through two hoses and controlled by

the power servo vacuum switch.

Defroster Door

The defroster door is in the defog position until vacuum

is applied to the actuator to obtain either full heat or full

de-ice position.

High Blower Delay Thermistor

The high blower delay thermistor is located on the

power servo housing under the power servo vacuum valve

and printed circuit board assemblies. The function of the

thermistor is to operate the blower at a reduced speed

when the control is in the HI FRONT position until the

residual cold air is discharged from the duct work. This

function occurs when the blower first comes "on" in cold

weather.

Vacuum Tank

During heavy acceleration, the vacuum supply from
the carburetor drops. The vacuum tank, using a^ check

valve, stores vacuum so that under these conditions

vacuum will be available for the Comfortron.

Thermal Vacuum Valve (Hot Water Vacuum Switch)

When engine coolant temperature reaches 75°F, the

valve opens and supplies vacuum to the outside air door

if the system is calling for outside air.

Master Delay Thermister

This thermistor delays the initial operation of the

blower when the system is in the heat mode. In cold

weather this allows outside ram air to flow through the

system thereby purging the cold air in the ducts gradually

until the coolant reaches about 105°F. Then, the termis-

tor passes enough current to energize the master delay

relay which powers the blower at about nine volts.

Vacuum Relay Valve

This relay valve will shut off transducer vacuum to the

power servo whenever the vacuum from the engine intake

manifold falls below the vacuum in the power servo

supply line (engine stopped or operating at low manifold

vacuum). This causes the power servo to be held in

position when the vacuum supply falls too low to maintain

servo control.

Vacuum Bleeder

A vacuum bleeder insures that the outside air door will

close (diaphragm will bleed down) after the system has

been shut down. This prevents outside air from entering

when starting the system on a cold day before the engine

coolant temperature reaches 75°F.

Sun—Ambient Sensor

The sun-ambient sensor measures the temperature of

the air entering the air intake grille in front of the wind-

shield. The sensor is exposed to sun light so that it can

lower the in-car temperature slightly when the sun

is shining.

Ambient Switch

The ambient switch operates the air conditioning com-

pressor clutch. When the outside temperature is above

40° F. the switch will be closed and the compressor will

be running. This switch is included as| part of the sun-

ambient sensor assembly, but operates independently.

Resistor Assembly

The blower resistors are located in the evaporator

housing. The printed circuit board switch in the power

servo determines which of the resistors is being used,

and as in conventional systems, the resistors control the

blower speed.

System Operation

When starting the Comfortron System in cold weather,

the following sequence of events occurs:

1.
Initially the system is inoperative. In LO FRONT

position the master delay thermistor is warming

(self-heating because current is flowing through it)

CHEVROLET CHASSIS SERVICE MANUAL

HEATER AND AIR CONDITIONING 1A-20

and its resistance is decreasing. In the HI FRONT

position, two thermistors (the master delay and high

blower delay thermistors) are warming. The air

door is in recirculation position until the engine

coolant reaches 75 degrees.

2.
The coolant reaches then 75 degrees and the thermal

vacuum valve opens applying vacuum to the air door

to admit outside air (unless the temperature dial is

set for cooling). Ram air will flow through the sys-

tem when the car is moving.

3.
Next, the master delay thermistor attains the tem-

perature at which it will pass sufficient current to

close the circuit through the master delay relay.

The relay circuit powers the blower motor at 9 volts.

4.
If the control is in the HI FRONT position, the high

blower delay thermistor will close the circuit

through the high blower relay which supplies full

available voltage to the blower motor. This function

occurs after the master delay thermistor has taken

effect because the high blower delay thermistor

uses the master delay type thermistor with a 10 ohm

1/4 watt resistor connected in
.
series. The nigh

blower delay thermistor must then warm to a higher

temperature than the master delay thermistor before

its resistance (plus that of the 10 ohm resistor)

drops enough to actuate the high blower relay.

5. If the controls are set for DE ICE, full outside air

and full voltage to the blower motor are effective

immediately regardless of temperatures or elapsed

times o

In accomplishing automatic control, the system follows

three steps to transform an electronic signal into me-

chanical energy through which the control is achieved.

Electronic Circuit

Two temperature sensors (Thermistors), and the duct

potentiometer connected in series, are located so as to

sense the temperature of the outside air, inside air and

system output air. The resistance of each sensor will

vary according to its temperature. The control head

temperature dial varies in resistance as it is adjusted by

the operator to suit his comfort requirements. The

resistance of the temperature dial control is applied

directly to the amplifier and is not in series with the

sensors and duct potentiometer. Thus temperature dif-

ferences in the sensor string plus the requirements fed

into the system by the operator cause changes in total

circuit resistance which allow a varying voltage flow

through the circuit.

Changing the Electronic Signal to Electrical Voltage

This minute voltage flow from the sensor string -

temperature dial circuit - is fed into the amplifier where

it is transformed into a usable amplifier output voltage,

the strength of which is determined by the strength of the

original amplifier input signal. This voltage is then

supplied to the transducer.

Changing the Electrical Voltage to a Vacuum Signal

Amplifier output voltage, varying according to tem-

perature requirements, is converted by the Transducer

into a modulator transducer output vacuum. This modu-

lated vacuum is applied to the Power Servo.

Changing the Vacuum Signal to Mechanical Energy

The Power Servo, controlled by the modulated Trans-
ducer output vacuum, operates the vacuum electrical and

mechanical components of the system as required to

provide automatic control of system operation.

Other major system components are mounted con-

ventionally in the engine compartment. Underhood com-

ponents and system airflow remain much the same as in

the Four-Season system except for the addition of the

automatic control provisions. The system operates on

100%
outside air, a mixture of outside and inside air, or

100%
recirculated air depending on the demands of the

system. The diaphragm operated .air selector door will

modulate outside air to the system during maximum air

conditioning requirements when the control unit is in

"Hi Front" position. Control of the blower is also com-

pletely automatic and dependent upon system demands.

Controls

The Comfortron controls the Chevrolet air conditioner

and heater in such a precise manner that the automobile

temperature remains relatively constant under all driving

conditions. By adjusting the thumb wheel on the Control

Head to any temperature desired between 65° and 85° F.

(See Figure 27) the automatic system will adjust the in-

car temperature even though the outside weather condi-

tions may vary considerably. The system will provide

maximum capacity for heating or cooling until the in-car

temperature reaches the pre-set Control Head Tempera-

ture. Where cooling is required, the system will start

immediately upon being turned "ON". During marginal

ambient temperatures the system will not always start

at the highest blower speeds of the control setting.

Therefore, occasionally the system can't be heard

starting*

Five over-riding functions are available so that special

conditions can be handled. Each Control Head function

will be discussed in detail below:

"Off" Position

In the "Off" position, the blower is turned off and the

outside air door is closed. No outside air should enter

the automobile.

"Lo Front" Position

The blower has five low to moderate speeds; Hi, M3,

M2,
M1 and Lo. The blower voltage will shift as directed

by the automatic controls. The "Lo Front" position

provides a quieter mode of automatic operation due to

reduction of blower noise.

"Hi Front" Position

The "Hi Front" position provides five high blower

speeds as called for by the automatic controls: The use

of the "Hi" blower speed results in a rapid cool down in

hot weather and rapid heating during cold weather. As

the in-car temperature approaches the temperature set-

ting on the Comfortron Control Head, the blower speed

will change, provided mild outside temperatures are

experienced. During very hot or cold weather, the blower

will reduce its speed only to the point where it is still

capable of maintaining the correct inrcar temperature.

"Rear" Position

The "Rear" position provides five high blower speeds.

The automatic controls select these speeds and blend the

discharge air to the proper temperature. By the use of

high blower speeds, increased airflow is obtained for

better rear seat passenger comfort.

CHEVROLET CHASSIS SERVICE MANUAL

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-22

RECEIVER &

OEHYDRATOR ASM
HOSES

CONDENSER

ASM.

Fig.
32—Universal System Components

Full right position will supply 100% outside air (for

heater operation) to the system while full left position

will provide 100% inside (recirculated) air for cooling

operation during city driving to shut out dust and fumes.

Recommended setting of this lever for most air con-

ditioning operations is about 1/4" to the right. This will

provide a mixture of recirculated air and outside air.

Fan Switch

The switch operates the three-speed blower motor.

Temperature Lever

This lever operates the damper door which controls

heater outlet temperature in the same manner as de-

scribed in the heater section.

"Two-Level"
Temperature Control

By moving the temperature lever to provide the desired

temperature on the floor, pulling the "Air Cond— Pull"

knob out halfway and moving the "Air" lever fully right

and setting the "Temp-Cool" knob for the desired breath

level temperature, "two-level" temperature control can

be maintained. This is especially desirable during

"marginal" weather conditions.
CORVETTE

The Corvette Four-Season Air Conditioning System, by

combining heating and cooling functions in a single unit,

provides maximum driving comfort during every season

of the year. Cooling and heating cores are mounted in

this "reheat" system in such a way that full outside air,

full recirculated air or a mixture, passes from the three-

speed blower through the evaporator (cooling) core and

then through and/or around the heater core. If the sys-

tem is not calling for heat all of the air flow will bypass

the heater core.

The cooling components of the system include the

compressor, condenser, receiver-d,ehydrator and evap-

orator together with the expansion valve and suction

throttling valve, all installed compactly beneath the

hood. The evaporator provides maximum cooling of the

system airflow when cooling is required. Cool airflow

is tempered by mixing warm air from the heater with

the cooled air from the evaporator. The PDA valve con-

trols evaporator pressure so that the unit may hold the

lowest pressure possible without danger of core freeze

up.

CHEVROLET CHASSIS SERVICE MANUAL

HEATER AND AIR CONDITIONING 1A-23

DEFROSTER

RECEIVER

DEHYDRATOR

EVAPORATOR

Fig.
33—All Weather System Components (Chevy II)

DEFROSTER OUTLETS
OUTSIDE
AIR
FROM PLENUM DUCT

BLOWER
--—-.

DEFROSTER

DOOR

HEATER OUTLET

AIR CONDITIONER "ON" DOOR

EVAPORATOR CORE

COLD
HEATER

CORE

AIR CONDITIONER

OUTLETS

AIR CONDITIONING

CONTROLS

AIR CONDITIONING

"ON"
KNOB
\ AIR DOOR

^CIRCULATED

m

AIR-FAN KNOB-

HEAT KNOB
HEAT DOOR

AIR

HEATER CONTROLS

IMJLJLII
""" L

—Mwm \

' / DASH PANEl

KNOB
DEFROSTER KNOB

Fig.
34-AH Weather System Schematic

CHEVROLET CHASSIS SERVICE MANUAL

HEATER AND AIR. CONDITIONING 1A-24

Fig. 35-Controls-AII Weather (Chevy II)

The heater components of the system are similar to

the standard Corvette heater with hoses routing engine

coolant to and from the heater core. A vacuum operated

shutoff valve assures that no coolant will pass through

the heater core until the system calls for heat.

Four control knobs surrounding the clock on the in-

strument panel center console provide full control of the

heating and cooling functions of the air conditioning

system.
The general arrangement of the system components

is pictured in Figure 37 while a schematic view of the

system will be found in Figure 36.

Controls Corvette

Four control knobs, grouped around the clock on the

instrument panel central console, provide full control

of the heating and cooling functions of the Corvette Air

Conditioning System. Each of the knobs, through a bowden

cable, operates one of the air diverter doors in the air

distributor assembly. In addition, the AIR COND.-PULL

knob operates the compressor switch; blower speeds are

controlled by turning the AIR PULL knob; and the heater

hot water valve vacuum switch is actuated by the COOL

IN-HQT PULL knob.

Air Conditioning "ON" Knob

The "AIR COND. PULL" knob controls the positioning

of the air diverter door which routes conditioned air

through either the dash diffuser ducts or the floor dis-

tributor outlets. Movement of this knob (hence, movement

of the selector door) also controls' the compressor

switch. When the door is positioned to send air through

the dash outlets the compressor is automatically turned

on to place the cooling system in operation and the fan

is turned on to LOW speed.

Blower Switch and Air Selector

The AIR PULL-FAN knob operates the selector door

in the right hand plenum chamber and may be set to allow

full outside air, full inside air, or a mixture of the two to

DEFROSTER DOOR

OPERATED BY

DEFROSTER KNOB
AIR CONDITIONING DOOR

OPERATED BY

AIR COND. PULL KNOB
BLOWER

OPERATED

BY TURNING

AIR KNOB

AIR DOOR

OPERATED

BY PULLING

AIR KNOB

OUTSIDE

AIR

CONTROLS

HEAT DOOR

OPERATED BY

COOL IN-HOT PULL

KNOB

L.H. OUTLET
CENTER

OUTLET
R.H. OUTLET
AIR COND.

PULL
COOL IN

HOT PULL

AIR PULL

LO-MED-HI
DEFROSTER

PULL

Fig.
36—Corvette Four-Season System Schematic

CHEVROLET CHASSIS SERVICE MANUAL

HEATER AND AIR CONDITIONING 1A-25

Fig.
37—-Corvette Four-Season System Components

pass through the system. For heating operations it is

suggested that Ml outside air (knob Mly OUT) be used.

For cooling operations under extreme heat conditions

push knob fully in (recirculated inside air); under moder-

ate temperature conditions pull the knob out to the detent

position (a misxture of outside air and inside air); and

under mild temperature conditions the knob may be

pulled fully out (outside air).

After the AIR PULL knob is set to permit air to pass

through the system, the knob may be rotated to control

the three-speed blower. When the AIR COND.-PULL

knob is pulled out the low blower is in operation. Select

higher speeds as desired.

Temperature Adjustment

The COOL IN-HOT PULL knob controls the air output

temperature during both heating and cooling operations.

A vacuum switch (operated by the temperature door

actuating cam) controls a vacuum operated water valve

which allows engine coolant to flow through the heater

core only when this knob is pulled out.

During heating operation cold ambient air enters the

conditioner, passes through the inoperative cooling core

and then passes through and around the heating core

(the final mixture of hot and cold air being determined

by the control knob - temperature door setting) and then

enters the car.

Cooling operation is exactly the same except that the

cooling core (evaporator) will be in operation at Ml

capacity, removing as much heat and humidity as pos-
sible from the warm ambient air flowing through it.

The COOL IN-HOT PULL knob may then be pulled out

as needed to temper this maximum cold airflow should

it become necessary.

Defroster Control

This control acts to divert heated air from the floor

distributor duct into the defroster duct for windshield

defogging, defrosting and deicing operations. A detent

is built into the defroster linkage to indicate the setting

at which a small portion of the heater air will be con-

tinaully passed over the windshield, thus keeping it clear.

Operating Instructions

Remember that the air conditioning system may be

used for heating or cooling during any season of the

year to provide just the desired comfort conditions.

Cooling

1.
"Air Cond-Pull". This knob should be pulled fully

out.

2.
"Cool In-Hot Pull". This knob should be pushed

fully in for maTriTr»"Tn cooling. Pulling out the knob

as required will mix warm air with the cool air to

temper the cool air output.

3.
"Air Pull-Fan". Set this knob fully in during ex-

treme heat conditions; at the detent position during

moderate temperature conditions; fully out during

mild temperature conditions or whenever tempering

of the cooled air flow is necessary. Turn the knob

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-27

POA SUCTION

THROTTLING
RTJING
^EXTERNAL

EQUALIZER LINE

COMPRESSOR

(Operates

continually

while system

is in operation)

M
H. P.
VAPOR
OIL BLEED LINE

SIGHT
,n

RECEIVERS

DEHYDRATOR

/

CONDENSER

EVAPORATOR

H.
P.
LIQUID
H
L. P.
LIQUID H] L.
P.
VAPOR
@ H. P.
POWER ELEMENT

III
•••••Mi
IM •—>•••—^

Fig.
38—Cycle
of
Operation—Four-Season and Comfortron

LINE
TO
COMPRESSOR

CLUTCH
THERMOSTATIC

SWITCH
v
CAPILLARY

* TUBING

EXPANSION

VALVE

SIGHT

GLASS

COMPRESSOR

(Operation

controlled

by thermostatic

switch)

I
H. P.
VAPOR

1
H. P.
LIQUID
aiJJ>1Tg.VW
RECEIVER

DEHYDRATOR

CONDENSER

EVAPORATOR

AVPSty>t*i"^if^

L.
P.
LIQUID

L.
P.
VAPOR
H.
P.
VAPOR POWER ELEMENT

Fig.
39-Cyc!e
of
Operation—Universal and All Weather

CHEVROLET CHASSIS SERVICE MANUAL