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 68 of 926
TM 9-2320-283-20-1
PRINCIPLES OF OPERATION.
1-15.
ELECTRICAL SYSTEM (Continued).
d.
Blackout Lighting System.
The blackout lighting system prevents operation of the horn and all service lighting, except instrument lamps.
The system
provides the following intensity lighting for operation:
(1) One blackout drive headlamp.
(2) Two front blackout marker lamps.
(3) Two taillamps and stoplamps.
(4) Trailer taillamps, stoplamps, and marker lamps at cab and chassis mounted 12-pin trailer connector.
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.
IGNITION
SWITCH.
Supplies 24-volt
power to
relay (RY-9), which in turn provides 12-volt power to electrical system,
including blackout lighting system.
BLACKOUT TOGGLE SWITCH.
Two-position switch for NORMAL and BLACKOUT modes of operation.
With this switch
in BLACKOUT position, 12-volt
battery power is available from headlamp switch to energize:
blackout headlamp, blackout
marker lamps, taillamps, and relays RY-4 and RY-5.
BLACKOUT HEADLAMP.
Consists of a single, replaceable sealed beam unit.
With headlamp switch in ON position, the
blackout headlamp is energized by 12-volt battery power.
BLACKOUT MARKER LAMPS.
Each consists of a replaceable bulb that is energized by 12-volt battery power when the
headlamp switch is in either ON position.
RELAY
(RY-4).
Normally open contacts are closed by 12-volt power when blackout toggle switch is in BLACKOUT
position.
When relay is energized, 24-volt power is supplied from circuit breaker CB-9 through 24-volt trailer connector.
RELAY
(RY-5). Normally open
contacts are
closed by
12-volt
power when blackout toggle switch is in BLACKOUT
position.
When relay is energized, 24-volt power is supplied from circuit breaker CB-8 through 24-volt trailer connector for
blackout taillamps.
CIRCUIT
BREAKER (CB-1).
Protects electrical components of stop switch circuit by opening when load exceeds 20
amperes.
May be manually reset by pressing CB-1 button in.
1-48
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