TM-9-2320-272-10
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; OPERATOR'S MANUAL
SEPTEMBER 2004
CHANGE 2
TM-9-2320-272-10 - Page 65 of 481
TM 9-2320-272-10
1-48
1-19. ELECTRICAL SYSTEMS OPERATION (Contd)
A
STARTER SOLENOID
– Junction point for battery positive lead (circuit 6)
and vehicle electrical feed wire (circuit 81).
a. Battery System Operation.
The battery system is identical for all models covered in this manual and
consists of the following major components and circuits:
B
CIRCUIT 6
– Connects the batteries to the starting motor and to the
protective control box through circuit 81.
C
BATTERIES
– Four 6TN batteries are connected in series parallel to provide
24-volts DC for the electrical starter system and 12-volts DC for the heater
fan low speed.
E
CIRCUIT 7
– Provides a ground between starter, battery, and chassis.
D
SLAVE RECEPTACLE
– Links an external power source directly to the
slaved vehicle’s batteries to assist in cranking the engine when the batteries
are not sufficiently charged.
F
PROTECTIVE CONTROL BOX
– Protects the vehicle electrical system in
the event the battery system polarity is reversed. Connects battery power to
vehicle electrical lead through circuit 81 and circuit 5. Connects positive
ground through circuit 94 to the starter.
G
BATTERY SWITCH
– Controls a relay in the protective control box through
circuit 459 that connects the batteries to the vehicle electrical load.
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