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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—^
^ S
N
RETAINING R I N G - ^
%
^
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
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