TM-9-2320-283-20-1
TRUCK TRACTOR, LINE HAUL, 50,000 GVWR, 6X4, M915A1
TECHNICAL MANUAL; ORGANIZATIONAL MAINTENANCE PART 1 OF 3
DECEMBER 1983
TM-9-2320-283-20-1 - Page 56 of 926
TM 9-2320-283-20-1
PRINCIPLES OF OPERATION.
1-15.
ELECTRICAL SYSTEM (Continued).
c.
Service Lighting System (Continued).
(2)
Marker and Clearance Lamps.
When headlamp switch is in either ON position and blackout toggle switch is in NORMAL position, 12-volt power is
supplied to illuminate clearance lamps, front marker lamps, and trailer marker lamps.
Trailer marker lamps receive power
through connectors mounted on cab and chassis.
BATTERY PACK.
Consists of four, 12-volt, maintenance free batteries.
Two batteries are wired in parallel
in each set.
Each set
is connected in series
for 24-volt output.
Battery pack
is used
for both 12-volt and 24-volt output.
CIRCUIT BREAKER (CB-7).
Protects 12-volt marker and clearance lamp switch circuit.
May be manually reset by
pushing button in.
HEADLAMP SWITCH.
Has one
OFF position
and two ON
positions.
Supplies 12-volt power in either ON position, to
clearance lamps, marker lamps, and 12-volt tractor connector when blackout toggle switch is in NORMAL position.
BLACKOUT TOGGLE SWITCH.
With toggle switch is set to NORMAL
position and headlamp switch is set to ON
position, 12-volt power is supplied to marker lamps, clearance lamps, and 12-volt tractor connector.
12-VOLT TRAILER CONNECTOR.
Seven-pin connector, containing 12-volt circuit for trailer clearance and marker lamps.
CLEARANCE LAMP SWITCH.
Provides capability of flashing clearance lamps on cab and 12-volts supplied to the tractor
connector, when switch is depressed and released.
12-volt power is supplied to switch when headlamp switch is in ON
position and blackout toggle switch is in NORMAL position.
CLEARANCE
LAMPS.
Each unit
has a
replaceable single-element bulb
that illuminates when headlamp switch is in
either ON position and blackout toggle
is
in
NORMAL
position.
The
clearance
lamps
will
flash when clearance lamp
switch is depressed and released.
MARKER LAMP ASSEMBLY.
Each assembly has two bulbs that illuminate whenever headlamp switch is in ON position
and blackout toggle switch is in NORMAL position.
One bulb
is used as a marker
lamp, and the other is
for turn signals.
RELAY (RY-6).
Normally open contacts are closed by 12-volt power when blackout toggle switch is in NORMAL position
and headlamp switch is in ON position.
When contacts of relay close, 24 volts from circuit breaker CB-9 is supplied to
tractor chassis connector.
1-36
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