Chevrolet 1977 light duty truck, Service Manual

Page: 845 / 861

O N - V E H I C L E SERVICE
M A IN T E N A N C E A N D
ADJUSTMENTS
T h e com ponents o f the Cruise-M aster System are
designed to be replaced should they become inoperative.
The Regulator is cali- brated in such a m a n n e r during
m a n u fa c tu rin g that overhaul operations are im practical.
However, one adjustm ent m ay be m ade to the Regulator
to correct speed d rop o r increase at the time o f
engagem ent.
R E G U LA TO R (FIG . 9-6C )
O ne regulator adjustm ent is possible - Engagem ent
C ruising Speed Zeroing (to remove any difference
between e n g a g e m e n t and cruising speed). N o regulator
adjustm ent should be m ade, however, until the Servo
Cable adjustm ent has been checked and vacuum hoses
are checked for leaks, kinks, or o th e r restrictions.
If the vehicle cruises at a speed a few mph above or
below the en g a g e m e n t speed, this erro r can be corrected
with a simple adjustm ent o f the orifice tube in the
regulator (fig. 9-2C).
CAUTION: Never remove orifice tube from
casting. It cannot be reinstalled once it has
been removed.
1. To check cruise speed error, engage Cruise-
M aster at 55 mph.
2. If vehicle cruises
screw orifice tube o u tw ard
3. If vehicle cruises
screw orifice tube inward
below engagem ent speed,
above engagem ent speed.
N O T E : Each 1/4 tu rn o f the orifice tube will
ch an g e cruise speed approxim ately one m ph. Snug-
up lock nut a fte r each adjustm ent.
I f a R egulator is fo u n d to be defective and not
simply out-of-adjustm ent, it must be replaced. D uring
replacement, check the hoses which connect to the
Regulator and replace any which are cracked or
deteriorated.
SERVO U N IT (FIG . 9-7C )
Before adjusting the Servo Cable, m ake sure the
carburetor is set at its lowest idle throttle position by
m anually setting the fast idle cam at its lowest step with
the ignition switch " O F F " . Adjust the cable so there is as
little lost motion at the Servo as possible (Fig. 9-7C).
If the Servo Unit is found to be defective,
replacem ent is required. N ote the condition o f the hoses
and replace any which are cracked or deteriorated.
BRAKE RELEASE SW ITC H E S (Fig. 9 -8 C )
Electric
The Cruise M aster brake release switch electrical
contacts must be switched open w hen the brake pedal is
depressed .38" to .64", measured at the brake pedal.
An inoperative switch must be replaced. Switch
replacem ent procedure is similar to standard brake lamp
switch replacement.
Vacuum
T he vacuum valve plunger must clear the pedal arm
w hen the arm is moved 5/1 6 inch, m easured at the
switch (fig. 9-9C).
An inoperative (sticking, plugged, o r leaking)
v acuum valve m ust be replaced. V acuum valve
replacem ent is sim ilar to brake lam p switch replacement.
Be certain that the hose to the valve is connected firmly
and is not cracked or deteriorated.
C O LU M N M O U N T E D E N G A G EM EN T
SW ITC H
T h e e n g a g e m e n t switch is serviced only by
replacem ent o f the turn signal lever assembly.
C O M PO NENT PART
REPLACEMENT
REG ULATO R
Replacement
1. Disconnect battery ground cable.
2. Disconnect speedom eter cables at regulator.
3. Disconnect vacuum and w iring harness at
regulator body.
4. Remove regulator to bracket screws and remove
regulator.
5. To install, reverse Steps 1-4 above.