CHEVROLET CAMARO 1967 1.G Chassis Workshop Manual

ACCESSORIES 15-2

GENERAL DESCRIPTION

The Cruise Master is a speed control system which

employs engine manifold vacuum to power the throttle

Servo unit. The Servo moves the throttle when speed

adjustment is necessary by receiving a varying amount

of bleed air from the Regulator unit. The Regulator

varies the amount of bleed air through a valve system

which is linked to a speedometer-like mechanism. The

speedometer cable from the transmission drives the

Regulator, and a cable from the Regulator drives the

instrument panel speedometer. The. engagement of the
Regulator unit is controlled by an Engagement Switch

located at the end of the turn signal lever. Two brake

release switches are provided: an Electric Switch dis-

engages the Regulator unit and a Vacuum Switch de-

creases the vacuum in the Servo unit to quickly return

the throttle to idle position.

The operation of each unit of the system and the

operation of the entire system under various circum-

stances is described below. Figure 1 shows the location

of the system components within the vehicle-

COMPONENT OPERATION

ENGAGEMENT SWITCH

This switch, located within the turn signal knob, has

three positions. In the fully released position, the switch

passes current through resistance wire to effect a "hold

in" magnetic field in the Regulator solenoid. This cur-

rent is sufficient only to hold the solenoid in place once

it has been actuated by the "pull in" circuit. Depressing

the button partially allows current to flow to the Regu-

lator solenoid at full voltage which causes the solenoid

to pull in. Depressing the button fully opens the circuit

to both the resistance and standard solenoid feed wires

and the solenoid becomes de-activated.

During vehicle operation the three switch positions

have the following functions:

Released

a. System not engaged: No function of the system

will occur although a small current is flowing

through the solenoid via the resistance wire (at

vehicle speeds over 20 mph).

b.
System engaged: The small current flowing

through the resistance wire is holding the solenoid

in the engaged position.

^r-WIRE RELIEF LUG

1 ^-#2-BLUE WIRE

L'3.BLACK WIRE
X /-TURN SIGNAL LEVER

SWITCH—^
^SN

RETAINING RING-^ %^

BUTTON -^

Fig.
2 - Cruise Master Engagement Switch
Partially Depressed

Full voltage is applied to the solenoid (vehicle speed

over 20 mph) which sets the Regulator to maintain the

vehicle speed at the time of Regulator engagement.

Fully Depressed

No electricity flows to the solenoid and the Regulator

is inactive. This position is used by the driver when he

desires to raise or lower his controlled speed. He may

accelerate to his new speed, press the button fully (Regu-

lator releases previously set speed) and release the but-

ton. Upon releasing the button, it passes through the

partially depressed position and the solenoid is "pulled

in", then into released position which provides "hold in"-

current. The driver may also press the button fully with

no pressure on the accelerator pedal. In this case the

regulator releases control of the throttle which returns

to idle and the car slows. When the button is released

the solenoid is pulled in and held in respectively and the

regulator resumes speed control at the speed of the

vehicle during the moment of button release (at vehicle

speeds over 20 mph).

LOCK
NUT

ORIFICE
TUBE

AND
CONNECTOR

ASSEMBLY

AIR FILTER AND

SOLENOID HOUSING COVER

Fig. 3 - Regulator Unit

CHEVROLET CHASSIS SERVICE MANUAL

ACCESSORIES 15-3

CONTROLLED AIR SUPPLY

FROM REGULATOR
DIAPHRAGM

SPRING

METERING ROD

VARIABLE ORF1CE

ENGINE AAANIFOLD VACUUM

FROM REGULATOR VACUUM VALVE
BEAD CHAIN

VACUUM CHAMBER —*
MOUNTING SCREW

Fig.
4- Servo Unit

BRAKE RELEASE SWITCHES

Two brake release switches are employed in the Cruise

Master System. When the brake pedal is depressed, an

Electric Release Switch cuts off the voltage supplied to

the engagement switch, hence cuts off power to the Regu-

lator unit. The Regulator is then disengaged and requires

Engagement Switch operation to return it to operation.

A Vacuum Release Switch operates simultaneously with

the electric release switch whenever the brake pedal is

depressed. This switch opens a port to atmospheric

pressure which rapidly bleeds down the vacuum in the

Servo unit thereby returning the throttle to the idle

position.

SERVO UNIT

The Servo unit is a vacuum actuated, variable position

diaphragm assembly which operates the carburetor throt-

tle when the system is in operation (fig. 4). It is powered

by engine intake manifold vacuum and operates the throt-

tle linkage via a bead chain. The Servo has two ports on

the sealed side of the diaphragm housing: one is supplied

manifold vacuum, and the other is connected to a variable

air bleed in the Regulator Unit. The vacuum port is

located at the center of the unit and the air bleed port

is near the outer wall. When vacuum is applied to the
center port, atmospheric pressure moves the diaphragm

which pulls on the bead chain opening the carburetor

throttle. As the diaphragm moves, it positions a tapered

needle within an orifice in the vacuum port so that as the

diaphragm moves toward the port, the orifice becomes

smaller; and as it moves away from the port, the orifice

becomes larger.

The air bleed port serves to supply a variable quantity

of air to the diaphragm chamber which causes the dia-

phragm to attain a balanced state (between the force of

the atmospheric pressure to chamber pressure differ-

ential and the force of the diaphragm and throttle return

springs). In operation then, the following events occur:

Vacuum is applied to the center port and the diaphragm

moves toward the port. The tapered needle restricts

the vacuum port more and more as it moves into the

orifice. If no air was allowed to bleed into the chamber,

the diaphragm would move until it contacted the housing,

however, the Regulator meters bleed air into the chamber

and the diaphragm reaches a point at which the air is

bled out of the chamber through the vacuum port orifice

as fast as it enters the air bleed port. If the Regulator

begins to supply less bleed air, (vehicle speed decreas-

ing) the vacuum in the chamber increases and the dia-

phragm moves toward the vacuum port. In so doing, the

tapered needle closes the vacuum port orifice even more

CHEVROLET CHASSIS SERVICE MANUAL

ACCESSORIES 15-4

Fig. 5 - Servo Mounting

and the air bled into the chamber again equals the air

bled out. A balance occurs again with the diaphragm in

a new position. If the Regulator begins to supply more

bleed air, (vehicle speed increasing) the vacuum in the

chamber drops and the diaphragm moves away from the

vacuum port, withdrawing the tapered needle from the

orifice and enlarging it. Since the vacuum orifice is

now larger, the greater quantity of air being bled into

the chamber may be bled out by vacuum and a balance

again occurs with the diaphragm in a new position.

AIR

TO SERVO

VACUUM

TO SERVO
VACUUM

RELEASE

SWITCH

ELEaRIC

RELEASE

SWITCH

Fig.
6- Servo, Regulator and Hose
Fig. 7 - Release Switches and Brackets

REGULATOR

The Regulator is a device which has two primary

functions: First, it is a vacuum switch which, when en-

gaged by the driver, supplies engine manifold vacuum to

the Servo. Second, it meters a small variable quantity

of air to the Servo unit in order to change the carburetor

throttle opening to effect speed control. A secondary

function of the Regulator is to drive the speedometer.

Since the car speed is sensed by a speedometer-like

mechanism within the unit, the speedometer cable from

the transmission drives the Regulator which drives a

second cable (at a one to one ratio) to the speedometer.

The Regulator is electrically engaged and disengaged

through operation of the Engagement Switch and the

Electric Brake Release Switch. It has two sub-assem-

blies which make up the unit: one being the magnetic

speed sensing assembly and the other being the solenoid

actuated vacuum switch, air bleed and filter, and low

limit speed switch assembly (fig. 8 and 9).

Magnetic Speed Sensing Assembly

The speed sensing assembly operates in the same man-

ner as a speedometer unit except that instead of rotating

a needle through an angle proportional to the vehicle

speed, it rotates a rubber drum which is clutched to the

air bleed valve when the system is in operation. The

assembly is driven by the speedometer cable from the

transmission which turns a disk shaped ferrite magnet.

Facing the magnetic disk is the driven brass disk mounted

on a shaft with the rubber drum mounted on the same

shaft. A spiral hairspring connects the shaft to the

housing and allows it to rotate through an angle which is

proportional to car speed. If the car doubled its speed,

the shaft would rotate to twice its previous angle as may

be seen by noting the operation of a speedometer. The

CHEVROLET CHASSIS SERVICE MANUAL

driven disk is sandwiched between the magnetic disk and

a field plate. The field plate forms a returning path for

the magnetic field from the magnetic disk.

The gear drive for the magnetic disk is a 90 degree

nylon gear drive with the driven gear rotating both the

magnetic disK and the speedometer drive cable.

Vacuum Switch, Air Bleed and Filter, and Low

Limit Speed Switch

The end of the shaft from the speed sensing assembly

with the rubber drum extends into the air bleed metering

assembly. This rubber drum has a tang extending from

its surface which allows a set of points to close at a

specific car speed. When the car reaches about 20 mph,

the rubber drum has rotated far enough (moved by the

brass driven disk in the magnetic field) so that its tang

has allowed a spring loaded electrical point to contact

another point. These points are in series with the sole-

noid coil so that under 20 mph, no Regulator operation

is possible.

Surrounding the rubber drum is a "U" shaped spring

clip which is held spread away from the drum by the

nose or cam of the solenoid when the solenoid is in the

relaxed position. The rubber drum and this clip com-

prise the speed clutch of the regulator. When the sole-

noid is energized, the solenoid nose moves toward the

drum and releases the ends of the clip. The clip springs

inward and attaches itself by friction to the drum. Now,
ACCESSORIES 15-5

any change in car speed will rotate the drum and move

the "U" clip just as a speedometer moves its needle.

The top of the MUtf clip is attached to the air bleed valve.

The clip moves a sleeve which slides on the orifice

tube thereby covering and uncovering air ports in the

wall of the tube (the tube inner end is plugged) whenever

car speed changes from the speed at which the solenoid

was energized. The direction of drum rotation is such

that resulting bleed valve operation will cause the Servo

to decrease engine power if the car exceeds the preset

speed and increase engine power if car speed decreases.

The air which passes out the orifice tube enters the

Regulator through the openings in the solenoid housing,

passes through the oil wetted polyurethane filter, and then

enters the orifice tube ports.

When the solenoid is de-energized, the nose retracts

and cams the ends of the "U" clip outward so that it re-

leases the rubber drum.

The solenoid also operates a vacuum switch simul-

taneously with the clutching and declutching of the "U"

clip.
The vacuum switch supplies the Servo unit with

manifold vacuum. The solenoid operated vacuum valve

slides over two ports in the Regulator wall. One port

is connected to manifold vacuum and the other is con-

nected to the center port of the Servo unit. When the

solenoid is de-energized, the valve closes the manifold

vacuum port and opens the Servo port to the inside of

the regulator case. When the solenoid is energized, the

valve connects the Servo port to the manifold vacuum

AAAGNET

SPEED CUP

FIELD PLATE

HAIRSPRING
TO SPEEDOMETER

MAGNET HOUSING

ASSEMBLY
ORIFICE TUBE &

CONNECTOR ASSEM.
CONTROL

VALVE

CLUTCH

SPRING

LOW LIMIT

SPEED SWITCH

RUBBER

DRUM

VACUUM PORT

TO SERVO

INPUT CONNECTION

SOLENOID COIL

SOLENOID AND CLUTCH

HOUSING ASSEMBLY
VACUUM PORT

TO ENGINE

VACUUM VALVE

UNLOCKING CAM

•SOLENOID PLUNGER

AIR FILTER

SIDE VIEW SECTION

REGULATOR DISENGAGED
END VIEW SECTION

ENGAGED

Fig.
8 - Regulator-Cross Section '

CHEVROLET CHASSIS SERVICE MANUAL

ACCESSORIES
15-6

port thereby supplying vacuum to the Servo unit.

During system operation
the
following events occur:

1.
Car
speed below
20
mph—no function
of the
unit

because
the
rubber drum
has
not rotated
far
enough

to close
the
solenoid points.
No
energizing current

can flow through the solenoid coil.

2.
Car
speed above
20
mph—The tang
on the
rubber

drum
has
closed
the
solenoid points
and
current
is

flowing through
the 40 ohm
resistance wire
to the

solenoid coil. This current
is
not sufficient to "pull

in", the solenoid.

3.
Driver partially presses Engagement Switch—full

voltage flows through
the
solenoid
to
pull
it
into

operation. Solenoid
cam
tension
on the "U"
clip
is

released and the clip grips the rubber drum. Simul-

taneously the vacuum switch operates; applying man-

ifold vacuum
to the
Servo unit which tightens
the

throttle chain. When
the
driver releases pressure

from
the
accelerator pedal
the
unit will position the

throttle
to
maintain the speed
at
the time
of
solenoid
operation.

Driver releases
the
Engagement Switch—current

flows
to the
solenoid through
the 40
ohm wire and

since the solenoid is "pulled in", the reduced current

flow
is
sufficient to hold
it
in position.

The
car
begins
to
ascend
a
hill—car speed drops

slightly (very slightly) and the magnetic force on the

driven disk
of the
speed sensor
is
decreased.
The

disk rotates slightly
(as
would
a
speedometer shaft

because
of
hairspring tension) turning
the
rubber

drum. Since
the "U"
clip
is
gripping
the
drum,
it

moves
the
slide which COVERS
the air
bleed ports

more. With less air bleeding into the Servo, greater

vacuum exists
in it
and the diaphragm moves toward

the vacuum port opening
the
throttle wider.
The

tapered needle moves into the orifice further and the

diaphragm balances
in a
new position with the wider

throttle opening.
Car
speed
has
been maintained

automatically.

1.
Speedometer Cable

Adapter (From

Transmission)

2.
Gasket

3. Speedometer Cable

Adapter
(To

Speedometer)

4.
Adapter
and
Magnet

Housing

5. Rotating Magnet

6. Helical Ramp
7. Field Plate Adjusting

Pinion

8. Adjusting Pinion

Locating Spring

9. Brass Magnetically

Driven Disk

10.
Field Plate

11.
Hair Spring

12.
Hair Spring Keeper

13.
Rubber Drum

Tang
14.
Rubber Drum

1$.
"U"
Shaped Clutch

Spring

16.
Air
Bleed Sleeve

17.
Orifice Tube

18.
Orifice

19.
Orifice Tube Locknut

20.
Clutch
and
Solenoid

Housing

21.
Vacuum Supply Port

(To Servo)
22.
Vacuum Port (To

Intake Manifold)

23.
Vacuum Valve Slide

24.
Solenoid Coil

25.
Solenoid Plunger

Return Spring

26.
Solenoid Cover Gasket

27.
Air Filter

28.
Solenoid Cover

29.
Air Inlets

Fig.
9-
Regulator
-
Exploded

CHEVROLET CHASSIS SERVICE MANUAL

ACCESSORIES 15-7

6. The car begins to descend a hill--car speed in-

creases slightly and the regulator movements oc-

curing above occur again except in reverse. The

rubber drum is turned further against spring tension

and the air bleed orifices are uncovered more. This

bleeds more air to the Servo reducing the vacuum in

the unit. The diaphragm moves away from the

vacuum port, closes the throttle slightly, and with-

draws the tapered needle from the vacuum orifice.

With the orifice enlarged, the increased vacuum

counteracts the increased air bleed and the dia-

phragm finds a balance again at a reduced throttle

opening.

7.
Driver accelerates by pressing accelerator pedal-

car speed increases and the system responds by

moving the diaphragm to decrease throttle opening.

Since a bead chain is used, the chain merely relaxes

and has no effect on throttle operation. After the

driver releases pressure from the pedal, the throttle

will close until car speed decreases to the pre-set

speed. At that point the Regulator bleeds less air

to the Servo which opens the throttle enough to

maintain the pre-set speed. The system returns to a

stable condition.

8. Driver desires higher controlled speed, presses ac-

celerator until new speed is reached, and depresses

Engagement Switch fully and releases button--speed

sensing assembly tries to turn in a direction that

would decrease the throttle opening until the driver

fully depresses the Engagement Switch. Then the

current is cut off to the solenoid which retracts; the

solenoid nose expands the "U" clip releasing its

grip on the rubber drum. The drum and disk as-

sembly then rotates to a new position because of the

higher car speed. When the solenoid retracts, it also

shuts off vacuum to the Servo and opens the vacuum

port to atmospheric pressure within the Regulator

thereby bleeding down the Servo toward idle throttle

position. As the driver releases the Engagement

Switch, the contacts cause "pull in" and "hold in" of

the solenoid respectively. The system is engaged to
maintain the car speed at the time of Engagement

Switch release.

9. Driver desires lower cruising speed, presses En-

gagement Switch fully, waits until car speed de-

creases to desired speed then releases Switch--when

the Engagement switch is fully depressed the sole-

noid is de-energized causing the vacuum switch to

bleed down the Servo to idle throttle position and the

"U"
clip of the idle bleed valve is released from the

rubber drum. The drum and disk assembly is free

to rotate to a position which corresponds to vehicle

speed as the car slows. When the driver releases

the Engagement Switch, the unit "pulls in" and "holds

in" in the normal manner. The air bleed valve is

clutched to, the rubber drum at the car speed during

switch release. Vacuum is again applied to the

Servo and throttle control is assumed by the Regu-

lator to maintain the car speed at the time of switch

release.

10.
With system in operation, driver applies brakes--

simultaneously the Vacuum Release and Electric

Release Switches operate. The Vacuum Switch

bleeds air into the Servo through the air bleed line

coming from the Regulator. The vacuum is reduced

in the Servo and the throttle returns to idle position.

The Electric Release Switch cuts off power to the

entire system and the solenoid is de-energized. If

the driver removes his foot from the brake pedal the

Electric Switch again feeds voltage to the Engage-

ment Switch and the Vacuum Switch seals the air

bleed line. If the vehicle speed is above 20 mph

when this occurs, reduced voltage will flow to the

solenoid through the 40 ohm wire which will not be

sufficient to "pull in" the unit. If vehicle speed is

below 20 mph no current will flow since the tang

on the rubber drum has opened the low limit switch

points in the Regulator. In either case, after de-

pressing the brake pedal, the system will not con-

trol car speed until the driver operates the engage-

ment switch above 20 mph.

SERVICE OPERATIONS

The components of the Cruise Master system are de-

signed to be replaced should they become inoperative.

The Regulator is calibrated in such a manner during

manufacturing that overhaul operations are impractical.

However, one adjustment may be made to the Regulator to

correct speed drop or increase at the time of

engagement.

BRAKE RELEASE SWITCHES

ELECTRIC

Service — An inoperative switch must be replaced.

Switch replacement is identical to standard brake lamp

switch replacement.

Adjustment- The brake switch plunger must clear the

pedal arm when the arm is moved 1/4 inch measured at

the switch (Figure 7).

VACUUM

Service
—
An inoperative (sticking, plugged, or leaking)

switch must be replaced. Switch replacement is similar
to brake switch replacement. Be certain that the hose to

the switch is connected firmly and is not cracked or

deteriorated.

Adjustment- The brake switch plunger must clear the

pedal arm when the arm is moved 5/16 inch measured at

the switch (Figure 7).

ENGAGEMENT SWITCH

Service

replacement.
The engagement is serviced only by

Removal

1.
Pry the engagement button out of the turn signal knob

with a small thin bladed screwdriver (Figure 2).

2.
With a small hook or long nosed pliers, remove the

switch retaining ring.

3.
.Pull switch outward utilizing the slack in the wiring

harness.

4.
With a small soldering iron, unsolder the wires and

resolder them to the correct terminals of the re-

placement switch.

CHEVROLET CHASSIS SERVICE MANUAL

ACCESSORIES
15-8

BROWN
BRAKE

SWITCH

+12V *

BLACK
CONNECTOR

AT FUSE BLOCK

CRUISE POSITION

BUTTON RELEASED

ENGAGE POSITION

BUTTON PARTIALLY DEPRESSED^ N. ENOAOi SWITCH

TRIM POSITION N. N. I

BUHON FULLY DEPRESSED. \ ^

BROWN

BLUE

ENGAGE SWITCH

CONFIGURATION

BLACK

BLUE

REGULATOR
- SOLENOID COIL

(5 a RESISTANCE)
9 BLACK

BLUE

REGULATOR

Fig.
10 - Wiring Diagram

Replacement

1.
Insert the switch into the turn signal knob, push the

retaining ring firmly against the switch, and push the

operating button onto the switch plunger. " .
SERVO

Service
—
H the Servo unit is found to be defective, re-

placement is required. Note the condition of the hoses

and replace any which are cracked or deteriorated.

CHEVROLET CHASSIS SERVICE MANUAL

ACCESSORIES 15-9

Adjustment- Adjust the bead chain so that it is as tight

as possible without holding the throttle open when the

carburetor is set at its lowest idle throttle position.

When connecting the bead chain (engine stopped) manually

set the fast idle cam at its lowest step and connect the

chain so that it does not hold the idle screw off the cam.

If the chain needs to be cut, cut it three beads beyond the

bead which pulls the linkage.

REGULATOR

Service - A defective regulator, that is one which is not

simply out of adjustment, must be replaced. During re-

placement, check the hoses which connect to the regulator

and replace any which are cracked or deteriorated.

Air Filter

The air filter located in the solenoid cover should be

cleaned and re-oiled at engine oil change intervals.

1.
Snap the solenoid cover off.

2.
Remove the filter and wash it in kerosene or mineral

spirits. Squeeze it dry and wet with SAE 10 engine

oil.
Squeeze out excess oil and reinstall into the

cover.

3.
Attach the cover with neoprene seal to the solenoid

housing. Be certain that the cover fits tightly to the

housing.

One regulator adjustment is possible: Engagement-

Cruising Speed Zeroing (to remove any difference be-

tween engagement and cruising speed).

NOTE:
No regulator adjustment should be

made, however, until the following items have

been checked or serviced:

1.
Bead chain properly adjusted.

2.
All hoses in good condition, properly attached, not

leaking, not pinched or kinked.

3.
Regulator air filter clean and properly oiled.

4.
Electric and vacuum release switches properly

adjusted.

Engagement—Cruising Speed Zeroing

If the cruising speed is lower than the engagement

speed, loosen the orifice tube locknut and turn the tube

outward; if higher, turn the tube inward. Each 1/8 turn

will alter the engagement-cruising speed difference one

mph. Tighten the locknut after adjustment and check the

system operation at 50 mph.

ELECTRICAL SYSTEM CHECK OUT

1.
Check fuse and connector.

2.
Check electric brake switch as follows: Unplug con-

nector at brake switch. Connect ohmmeter at points

A and B on brake switch. The ohmmeter must indi-

cate infinity when the brake pedal is depressed and

continuity when pedal is released. The cruise re-

lease brake switch (electric) is adjusted as is the

standard stop light brake switch. Replace electric

brake switch if needed.

3.
Check engagement switch and connecting wiring as
follows: Unplug push button control connector

(brown, blue, black) at electrical wiring harness con-

nector and perform the following tests. (See Fig-

ure 10)

Test #1
—
Connect ohmmeter between terminal #1 (brown

wire) and terminal #2 (blue wire). Continuity shall be

maintained until switch is depressed all the way in.

Test #2
—
Connect ohmmeter between terminal #1 (brown

wire) and terminal #3 (black). No continuity shall be

shown; however, when the button is depressed halfway,

continuity shall be indicated. When the button is pressed

all the way down, no continuity shall be shown.

Test #3 — Connect ohmmeter between terminal #2 (blue

wire) and terminal #3 (black). Button released, no con-

tinuity; however, when the button is depressed partially

and fully, continuity shall be shown.

4.
Check regulator solenoid coil, low-speed switch, and

wiring harness as follows:

a. Disconnect engagement switch wire harness con-

nector from the main wire harness connector

(brown, blue, and black wires). Connect ohm-

meter
'
between point C (blue wire in main wire

harness) and ground. (Make sure the regulator is

well grounded to chassis.) The ohmmeter should

read 45 ohms ± 2 ohms. If a resistance of

greater value is shown, then disconnect the con-

nector from the regulator and measure the re-

sistance of the blue wire from point C to D. It

should measure 40 ohms. Check the resistance

from point E (vertical bar of terminal forming T)

to ground. It should measure 5 ohms ± 1/4 ohm.

Replace either the wiring harness or solenoid as

needed if greater values are indicated. The black

harness wiring from point F to G should also be

checked for continuity.

ENGAGEMENT SWITCH TEST

BUTTON POSITION

Cruise (released)

Engage (partially depressed)

Trim (fully depressed)
TERMINALS

1 TO 2

closed

Closed

open
1 TO 3

open

closed

open
2 TO 3

open

closed

closed

SERVO AND VACUUM SYSTEM CHECK OUT

To determine the condition of the diaphragm, remove

hoses from power unit and apply 14 inches of vacuum to

either vacuum tube opening (seal the other opening) and

hold in for one minute. The vacuum shall not leak down

more than 5 inches of vacuum in one minute. If leakage

is detected, replace servo. To utilize engine as a vac-

uum source, proceed as follows:

1.
DISCONNECT SERVO $EAD CHAIN and hoses from

servo and connect engine vacuum directly to vacuum

servo fitting (fitting in middle of servo). Seal the

servo unit opening.

2.
Note position of servo diaphragm.

3.
Start engine - the diaphragm should pull in.

4.
Clamp off engine vacuum supply line and check for

leakage. '

The cruise release brake switch (vacuum) and connecting

hoses can likewise be checked using a vacuum pump.

CHEVROLET CHASSIS SERVICE MANUAL

CRUISE MASTER SYSTEM CHECKS

Will not engage

Does not cruise at engage-

ment speed

System hunts or pulses

System does not disengage -

with brake pedal

System applies full throtUe

when engaged

Cannot adjust speed down-

ward with Engage Button

Does not engage or engages

lower than limits referred

to in "Driver Operation"
Cause

Brake Switch Circuit Open

Fuse blown

Defective Engage Switch

Vacuum leak in Servo and/or Brake

Switch and connecting lines.

Open in wiring harness

Defective Regulator

Orifice Tube misadjusted

Bead Chain loose.

Kinked or deteriorated hoses

Dirty Air Filter

Defective and/or improperly posi-

tioned Drive Cables and/or Casing

Assemblies

Defective Regulator

Brake and/or Vacuum Switch mis-

adjusted or defective

Hoses interchanged at Servo

Defective Regulator

Defective Engagement Switch or

Wiring

Internally Misadjusted Regulator
Correction

Check connections - adjust or replace switch. Refer to

Electrical Check Out.

Replace fuse - if it blows again, check for:

1.
Engage Switch stuck in the center of travel - Refer

to Electrical Check Out.

2.
Incorrect wiring - Refer to Electrical Check Out.

3.
Short to ground - Refer to Electrical Check Out.

Make necessary corrections.

Replace as needed - Refer to Electrical Check Out.

Vacuum test and repair or replace as needed. Refer to

Servo and Vacuum System Check Out.

Repair or replace as needed.

Replace Regulator.

Adjust as required.

Tighten Bead Chain.

Repair or replace.

Service as required.

Repair or replace as needed.

Replace Regulator.

Adjust or replace as required. Refer to Servo

and Vacuum System Check Out and Electrical Check

Out.

Correct as needed.

Replace Regulator.

Replace as needed. Refer to Electrical Check Out.

Replace Regulator

ACCESSORIES 15-11

12 VOLTS D.C.
ELECTRIC BRAKE

RELEASE

IGNITION

SWITCH

ENGINE

VACUUM

TRANSDUCER

Fig.
11 - Vacuum and Electrical Diagram

AUTOMATIC LEVEL CONTROL

INDEX

Page

General Description . . 15-11

System Checks and Adjustments 15-13

Service Operation . 15-15

GENERAL DESCRIPTION

A pneumatic level control system that automatically

maintains correct rear trim height of a car under varying

load conditions, the optional automatic level control is

used only in conjunction with the Superlift Shock Absorber

option.

The Superlift Shock Absorber option alone, consists of

the two shock absorbers with pressure lines to a "Tee"

where a ill valve is located, the shocks are inflated

with (or deflated of) compressed air (at any gas station)

to obtain the vehicle level desired with any given load

change.

The automatic leveling system is added to the Superlift

Shock Absorbers and supplies its own compressed air.

The system (fig. 13) consists of a vacuum operated air

compressor with pressure regulator,
and
integral storage

tank, vacuum line to engine, air intake filter, air lines,

and a height control valve.

The COMPRESSOR is a two-stage, vacuum actuated

type, requiring no lubrication. Vacuum supply is taken

from engine carburetor base. High pressure air is
supplied to the reservoir tank by the second stage of

the two-stage compressor. The first stage intake stroke

draws air at atmospheric pressure through a oneway

check valve located in the end of the first stage housing

under the first ^tagei housing cover. On the first stage

compression stroke, the intake valve is closed and the

oneway check valve in the second stage end of the piston

is opened. This allows the air from the first stage

cylinder to flow through the hollow piston into the second

stage cylinder for jhigh pressure compression. The

second stage compression stroke closes the check valve

in the piston and opeijis the check valve in the end of the

second stage housing.

The intake and compression strokes are controlled by a

sliding distributor valive that is actuated through an arm

that is tripped by the piston as it nears the end of each

stroke. Each time the arm actuates the distributor

valve, a different set of holes are covered in the first

stage housing. The distributor valve controls the flow of

intake manifold vacuum and air under atmospheric pres-

CHEVROLET CHASSIS SERVICE MANUAL