1967 CHEVROLET CAMARO coolant

LUBRICATION 0-14

SAE 5W-30 oils may be used during periods when

temperatures of 32° and below are to be expected.

Types of Oils

In service, crankcase oils may form sludge and varnish

and under some conditions, corrosive acids unless pro-

tected against oxidation.

To minimize the formation of these harmful products

and to assure the use of oil best suited for present day

operating conditions, automobile manufacturers have de-

veloped a series of sequence tests designed to evaluate

the ability of any oil to properly lubricate automobile

engines.

It is recommended that only those oils which are

certified by their suppliers as meeting or exceeding the

maximum severity requirements of these sequence tests

(or GM Standard 4745-M) be used in Chevrolet engines.

Certified sequence tested oils will be described as such

on their containers.

Maintaining Oil Level

The oil gauge rod is marked "Full" and "Add Oil."

These notations have broad arrows pointing to the level

lines.
The oil level should be maintained between the

two lines, neither going above the "Full" line nor under

the "Add Oil" line. DO NOT OVERFILL. After operating

vehicle allow a few minutes for oil to return to crankcase

before checking oil level.

Check the oil level frequently and add oil when

necessary.

Oil and Filter Change Intervals

NOTE:
Under prolonged dusty driving condi-

tions,
it is recommended that these operations

be performed more often.

OIL

To insure continuation of best performance, low main-

tenance cost and long engine life, it is necessary to

change the crankcase oil whenever it becomes contami-

nated with harmful foreign materials. Under normal

driving conditions draining the crankcase and refilling

with fresh oil every 60 days or every 6000 miles which-

ever occurs first, is recommended.

It is always advisable to drain the crankcase only after

the engine has become thoroughly warmed up or reached

normal operating temperature. The benefit of draining is,

to a large extent, lost if the crankcase is drained when

the engine is cold, as some of the suspended foreign

material will cling to the sides of the oil pan and will not

drain out readily with the cold, slower moving oil.

OIL FILTER

Change engine oil filter every 6000 miles or every 6

months, whichever occurs first.

NOTE:
For Vehicles in heavy duty operation

involving continuous start-stop or prolonged idl-

ing, engine oil should be changed after 2500-

3000 miles of operation. The filter should be

changed after 5000-6000 miles of operation.
Crankcase Dilution

Probably the most serious phase of engine oil deterio-

ration is that of crankcase dilution which is the thinning

of the oil by fuel vapor leaking by pistons and rings and

mixing with the oil and by condensation of water on the

cylinder walls and crankcase.

Leakage of fuel, or fuel vapors, into the oil pan occurs

mostly during the "warming up" period when the fuel is

not thoroughly vaporized and burned. Water vapor enters

the crankcase through normal engine ventilation and

through exhaust gas blow-by. When the engine is not

completely warmed up, these vapors condense, combine

with the condensed fuel and exhaust gases and form acid

compounds in the crankcase.

As long as the gases and internal walls of the crank-

case are hot enough to keep water vapor from con-

densing, no harm will result. However, when the engine

is run in low temperatures moisture will collect and

unite with the gases formed by combustion resulting in

an acid formation. The acid thus formed is likely to

cause serious etching or pitting which will manifest itself

in excessively rapid wear on piston pins, camshaft

bearings and other moving parts of the engine, oftentimes

causing the owner to blame the car manufacturer or the

lubricating oil when in reality the trouble may be traced

back to the character of fuel used, or a condition of the

engine such as excessive blowby or improper carburetor

adjustment.

Automatic Control Devices to Minimize

Crankcase Dilution

All engines are equipped with automatic devices which

aid greatly in minimizing the danger of crankcase

dUution.

The thermostat, mounted in the cylinder head water

outlet, restricts the flow of water to the radiator until a

predetermined temperature is reached, thus minimizing

the length of time required to reach efficient operating

temperature, reducing the time that engine temperatures

are conducive to vapor condensation.

A water by-pass is included in the cooling system,

utilizing a hole in the front of, the cylinder block. This

allows a limited circulation of coolant, bypassing the

thermostat until thermostat opening temperatures are

reached. This system provides a uniform coolant tem-

perature throughout the engine, eliminating localized

hot-spots, improving exhaust valve life, provides fast

warmrup of lubricating oil and fast temperature rise in

the coolant which provides fast heater operation in cold

weather.

A thermostatic heat control on the exhaust manifold

during the warming up period, automatically directs the

hot exhaust gases against the center of the intake mani-

fold, greatly aids in proper vaporization of the fuel.

An automatic choke reduces the danger of raw or

unvaporized fuel entering the combustion chamber and

leaking into the oil reservoir.

An.
efficient crankcase ventilating system drives off

fuel vapors and aids in the evaporation of the raw fuel

and water which may find its way into the oil pan.

CRANKCASE BREATHER CAP

Clean and re-oil at every oil change..

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-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-33

within the system. The following fixed conditions must be

adhered to in order to make it possible to compare the

performance of the system being tested with the stan-

dards below:

1.
Doors and windows closed. (Car inside or in shade.)

2.
Hood up and engine exhaust suitably ventilated.

3.
Vehicle in NEUTRAL with engine running at 2000

rpm.

4.
Air Conditioning controls set for -

• Maximum cooling.

• High blower speed.

5.
TEMP knob and AIR knob set for full recirculating

air. On Comfortron systems* move the control lever

to REAR and pull the white vacuum hose from the

transducer. Plug the hose. An alternate method is to

install the J-22368 Tester (described later in this

section) and operate it on MANUAL control to main-

tain maximum cooling and blower speed.

6. Gauge set installed.

7.
System settled out (run-in approximately
10
minutes).

8. A thermometer placed in front of vehicle grille and

another in the right hand diffuser outlet.

PERFORMANCE DATA

The following Performance Data define normal opera-

tion of the system under the above conditions. Relative

humidity does not appear in the tables because after

running the prescribed length of time on recirculated air

and maximum cooling, the relative humidity of the air

passing over the evaporator core will remain at ap-

proximately 35% to 40% regardless of the ambient

temperature or humidity.

Should excessive head pressures be encountered at

higher ambient temperatures, an 18" fan placed in front

of the vehicle and blowing into the condenser will provide

the extra circulation of air needed to bring the pressures

to within the limits specified.

NOTE: Higher temperatures and pressures will

occur at higher ambient temperatures, fti areas

of high humidity it is possible to have ther-

mometer and gauge readings approach but not

reach the figures listed in the performance

tables and still have a satisfactory operating

unit. However, it is important to remember that

low pressure has a direct relationship to nozzle

outlet temperature. If pressure is too low, ice

will gradually form on the evaporator fins, re-

stricting airflow into the passenger area and

resulting in insufficient or no cooling.

Four-Season and Comfortron System

Chevrolet and Camaro
Chevelle

(Refrigerant
Charge
=

Temperature
of Air

Entering Condenser

Engine rpm

Compressor

Head Pressure

Evaporator Pressure

at POA

Discharge Air Temp,

at Right Hand Outlet
3
Lbs. -

70°

145-

155

38-

41
80°

170-

180
12 02

90°
.)

100°

2000

205-

215

29.5 -

39-

42
41-

43
255-

265

30.5

42-

45
110°

260-

270

psi

43-

46
120°

295-

305

45-

48
(Refrigerant Charge =

Temperature of

Air Entering

Condenser

Engine rpm

Compressor Head

Pressure

Evaporator
Pressure

at
POA

Discharge Air

Temp, at Right

Hand Outlet
3 Lbs. -

70°

150

160

37-

40
80°

175

185
12 Oz.)

90° 100°

2000

210 250

220 260

29.5 - 30.5

37-

40
38-
39-

41 42
110°

280

290

psi

40-

44
120°

290

300

41-

45

Corvette

(Refrigerant Charge =

Temp, of Air

Entering Condenser

Engine rpm

Compressor

Head Pressure

Evaporator
Pressure

at
POA

Outlet
Air

Temperature

(at Right
Outlet)
3
Lbs.

70°

150-

170

38-

40
- 4 Oz.)

80°

175-

195

29

38-

40
90°

2000

200-

200
100°

i*pm

240-

260
110°

285-

300

5-
30.5 psi

40-

42
41-

43
43-

45
120°

325-

335

45-

47

Alt Weather System

Chevy II

(Refrigerant
Charge
=

Grille Air

Temperature

Engine rpm

Compressor Head

Pressure

Compressor Suction

Pressure**

Discharge Air Temp,

at R/H Outlet**
2-1/2 Lbs.)

70°

120-

140

13

32-

37
80°

150-

160

14
CO
OO
CO
CO
90°
100°

1500

175-

185

15

35-

40
220-

230

15

36-

41
110°

240-

250

19

37-

42
120°

265-

275

19

38-

43

**When Compressor Clutch Releases

COMFORTRON SYSTEM OPERATIONAL TEST

This test, designed as a quick check of total system

operation, must be made with the engine operating at

minimum of 2000 rpm and coolant warm. Wait several

seconds between operations to allow the system to move

through its sequence of operation and arrive at the pre-

scribed mode of operation.

1.
With control lever in the OFF position, and Tem-

perature Dial at 65°F.

a. System is turned OFF, there is no air flow from

any of outlets.

2.
Control lever in HI Front and Temperature Dial set

at65°F.

CHEVROLET CHASSIS SERVICE MANUAL

HEATER AND AIR CONDITIONING 1A-37

VACUUM SYSTEM COMPONENT FUNCTION

Component

Air Door Diaphragm

Power Servo

Vacuum Relay Valve

Mode Door Diaphragm

Defroster Diaphragm

Transducer

Thermo Vacuum Valve
Vacuum Applied

Air Door Open to Outside Air

(Closed to Car Body)

Maximum Heat

Vacuum Applied to One Port Opens a Passage

Through the Valve to Allow Transducer Vacuum

to be Supplied to the Power Servo

Vacuum to Linkage Side

Air Flow Out Heater

Ducts

Full Airflow Out Heater

Outlet
Vacuum to Covered Side

Airflow Out of Upper

Outlets

Full Airflow Out Defroster

Outlets (Full De-ice)
No Vacuum Applied

Air Door Open to

Re circulated Air

(Open to Car Body)

Maximum Cooling

No Vacuum Applied Closes

Vacuum Supply to Power

Servo

Airflow Out of Upper and

Lower Outlets Door Open

1"
from 100% Lower Out-

let Position

Airflow Divided 1/3 Out

Defroster Outlets 2/3

Out Heater Outlets

Supplies Modulated Vacuum to Power Servo

Zero Voltage Applied to Transducer

Results in Maximum Vacuum Supply
10 Volts Applied to Transducer

Results in No Vacuum Supply

(Coolant Hot) Passes Vacuum When System is Calling For Outside Air

MAINTENANCE AND ADJUSTMENTS

EVAPORATOR CONTROL VALVE (POA)

(Chevrolet, Chevelle, Comoro, and Corvette

Four Season) (Chevrolet Comfortron)

The only check for proper POA valve operation is to

check the suction pressure at the valve as during a

performance test. The POA valve is an absolute valve

and will provide different gauge readings based on the

altitude where the readings are being taken. Correct

gauge reading at sea level is 29.5 psig. Gauge readings

will be one-half psi higher for each additional 1000 feet

of elevation. The following table lists gauge readings at

different altitudes. If a valve gives improper gauge

readings, it must be replaced since it is not repairable

or adjustable.

29.5

30.0

30.5

31.0

31.5

32.0

32.5

33.0

33.5

34.0

34.5
psig.

psig.

psig.

psig.

psig.

psig.

psig.

psig.

psig.

psig.

psig.
— Sea 1

— 1000

— 2000

— 3000

— 4000

— 5000

— 6000

— 7000

— 8000

— 9000
Level

ft.

ft.

ft.

ft.

ft.

ft.

ft.

ft.

ft.

— 10000 ft.
THERMOSTATIC SWITCH

(Universal and Chevy II All-Weather System)

Thermostatic switches used in Universal and All-

Weather systems differ only in the capillary tube sensing

unit.

The Chevy n All-Weather System thermostatic switch

has an air sensing capillary which is coiled and attached

to the front of the evaporator core with plastic plugs.

This type of unit is controlled by the temperature of the

air leaving the evaporator.

Universal systems make use of a thermostatic switch

with a fin sensing capillary or a self-supporting air sens-

ing capillary. This capillary controls the switch by

sensing the temperature of the metal fins or the air

leaving the fins.

Checking for Proper Operation

1.
Install the gauge set and set up the vehicle as

described under Performance Test.

2.
Movement of the temperature control knob should

result in a definite change in suction pressure and

cycling of the compressor clutch.

• If compressor continues to operate regardless of

the knob adjustment, it indicates that the points

CHEVROLET CHASSIS SERVICE MANUAL