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Sec. 7
Page 112
GM COACH MAINTENANCE MANUAL
WIRING AND MISC. ELEC.
SOLENOIDS AND MAGNET VALVE
A solenoid is an electrical device used to op-
erate a unit to which it is mechanically connected.
When solenoid coils are energized by completing
electrical circuit through its controlling switch,
solenoid plunger is pulled into coils, thereby op-
erating the unit to which the solenoid plunger is
attached.
ENGINE STOP SOLENOID
Engine stop solenoid is mounted on engine
governor and is connected to governor cam. Sole-
noid, when energized by placing control switch in
"STOP" position, moves governor cam, allowing
governor to move injectors into no-fuel position.
Refer to ENGINE (SEC. 8) for illustration showing
solenoid installation.
EMERGENCY STOP SOLENOID
Emergency stop solenoid, mounted on blower
intake, is used to release a valve to shut off air
supply to engine, thereby stopping engine. Sole-
noid is energized through an "EMERGENCY STOP"
switch on driver's control panel. When solenoid
is energized, the solenoid plunger raises away
from release cam on air choke valve, permitting
the air choke valve to close.
NOTE: Whenever engine is stopped by
releasing the air choke valve, valve must
be reset by hand before engine can be
started.
REVERSE SOLENOID
The reverse solenoid, mounted on transmis-
sion, is used to move shift finger into engagement
with reverse shift fork so shift into reverse can
be accomplished.
Reverse solenoid has two coils, the pulling
coil and the holding coil.
Electrical circuit to
solenoid is controlled by a relay, mounted on en-
gine compartment control panel, and a "REVERSE
SELECTOR" switch on control panel at left of
driver.
Refer to TRANSMISSION (SEC. 17) for illus-
tration showing solenoid and linkage.
ST ARTER SOLENOID
Starter solenoid is mounted on starter and
solenoid plunger is connected to starter shift lever
by a link (fig. 16). In addition to shifting starter
pinion into engagement with flywheel ring gear,
solenoid also completes circuit direct from bat-
tery to starter.
Solenoid circuit is controlled by
"START" switch on driver's control panel or on
engine compartment panel, and a relay mounted
on engine compartment panel.
Refer to "Engine
Control and Generator Wiring Diagram" in back
of manual for starter circuit.
Solenoid has two coils. The pulling coil draws
comparatively heavy current for a short interval.
This is needed to shift pinion into engagement with
flywheel ring gear. The holding coil also aids the
pulling coil.
As soon as the shift is completed
and the solenoid contacts complete the starter cir-
cuit, the pulling coil is de-energized by action of
the solenoid contacts and only the holding coil
continues to draw current.
SOLENOID MAINTENANCE
Solenoids require no maintenance other than
keeping contact points and terminals clean and
tight.
Always check action of solenoid if it has
been removed and reinstalled.
If
solenoid fails to
function, first check switches, relays, and wiring
before working on solenoid.
Solenoid
current
draw can be tested, using suitable test equipment.
Correct current draw values for all solenoids are
listed in "Specifications" at end of this group.
SOLENOID LINKAGE ADJUSTMENT
Refer to ENGINE (SEC. 8) for adjustment of
engine stop and emergency stop solenoids. Refer
to "STARTER" later in this group for starter
solenoid linkage adjustment. Refer to TRANSMIS-
SION (SEC. 17) for reverse solenoid linkage ad-
justment.
INJECTOR SHUT-OFF MAGNET
VALVE
Magnet valve is used in conjunction with air-
operated injector shut-off system to control the
air pressure used for operation of the air cyl-
inder.
Wiring connections are shown on "Air
Injector Shut-Off and Motor-Gard Wiring Diagram"
in back of manual.
Installation of magnet valve,
together with a sectional view of the unit, are
illustrated in DIESEL ENGINE (SEC. 8).
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