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GM COACH MAINTENANCE MANUAL
Sec. 7
Page 109
NOTE:
When starting engine, circuit
through low oil pressure switch is immedi-
ately completed, and Moto-Gard heating el-
ement starts to heat up as soon as control
switch is placed in
"RUN"
position. If en-
gine fails to start during time required
for Moto-Gard contacts to close (25 to 35
seconds), Moto-Gard will cause injector
racks to be moved to no-fuel position. It
is then nec~ssary to turn control switch
off and wait approximately 30 seconds for
Moto-Gard heating element to cool, then
place control switch in "RUN" position and
again attempt to start engine.
WIRING AND MISC. ELEC.
MOTO-GARD TEST
Start engine and run for a few minutes to build
up pressure in air system. Open engine compart-
ment door at rear of vehicle. Ground engine over-
heat thermostat terminal and check time lapse be-
fore Moto-Gard acts to stop engine. Time should
be 25 to 35 seconds.
If longer time is required,
Moto-Gard requires adjustment. If engine does
not stop within one minute, Moto-Gard system is
not functioning.
Check relay and magnet valve
operation and repair or replace if necessary.
If
Moto-Gard system still fails to stop engine, re-
place Moto-Gard unit.
RELAYS
Relays are magnetic switches used to provide
control for numerous electrical circuits. Through
the use of a relay,
it
is possible to automatically
open or close a circuit as operating conditions
may require. Usually when a relay is used, it is
possible to eliminate great lengths of heavy cable,
thereby providing higher voltage to operating units.
Some relays used on these vehicles are the same
even though they are used in different circuits
and for different purposes.
Relay contacts may
be cleaned with a fine cut contact file.
Refer to Wiring Diagrams in back of manual
for wire size and color, junction terminals, and
relay terminal identification.
LIGHTING, REVERSE, STARTER,
AND BLOWER RELAYS
Relays used in the general and reading light
circuits, starter circuit, and blower circuit are
all identical.
Lighting relays are mounted on
driver's front trim panel (fig. 5).
Reverse and
starter relays are mounted on engine compartment
control panel (fig. 4).
Blower relay is mounted
behind control panel at left of driver (fig. 7).
Figure 7-Driver's Control Panel Removed
for
Access
to Relays
Relay used in these circuits is illustrated in fig-
ure 8.
Relay points are normally open.
When
circuit is completed through relay winding, arma-
ture is attracted to core and points close. This
completes circuit from "BAT" terminal through
the points and the "VAC" terminal to the operating
unit.
ADJUSTMENTS
Refer to "Specifications" at end of this group
for air gap and point opening dimensions and for
closing voltage.
Air Gap (Fig. 8)
Disconnect lead from "BAT" terminal.
With
contact points held closed, measure air gap be-
tween armature and center of coil. Adjust air gap
by loosening two screws and moving armature up
or down as required. If necessary, align the sup-
port carrying the lower contact so the air gap will
be uniform between the coil and the armature.
AIR GAP
COIL
AIR GAP ADJUSTMENT
TP 0825-2
Figure 8-Relay Used in Lighting, Reverse, Starter, Blower,
and Heater Circuits
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