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 68 of 481
TM 9-2320-272-10
1-51
1-19. ELECTRICAL SYSTEMS OPERATION (Contd)
d. Generating System Operation.
The generating system is identical for all vehicles covered in this manual and
consists of the following major components and circuitry:
F
VOLTMETER
– Indicates electrical system voltage. It is connected to the
electrical system through circuit 27.
G
ALTERNATOR
– Rated at 26-30 volts, 60 amperes, the alternator assists
and recharges the batteries during operation. A 100 ampere model is
available as a kit.
H
CIRCUIT 3
– Provides a ground circuit to the alternator.
J
CIRCUIT 568
– Senses system voltage and excites the alternator field.
I
CIRCUIT 566
– Controls a relay in the protective control box that prevents
the starter from reactivating while the engine is running.
L
CIRCUIT 5
– Conducts alternator output to charge the batteries and
maintain vehicle voltage.
K
PROTECTIVE CONTROL BOX
– Connects circuit 5 to 81 to power the
electrical system and charge the batteries.
M
BATTERY SWITCH
– Closes the relay in the protective control box that
connects battery circuits.
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