TM-9-2320-280-20-1
TRUCK, UTILITY: M998 SERIES
TECHNICAL MANUAL; UNIT MAINTENANCE; VOLUME 1 OF 3
JANUARY 1996
TM-9-2320-280-20-1 - Page 75 of 888
TM 9-2320-280-20-1
Change 1
1-42.3/(1-42.4 blank)
1 - 2 3 . 3 . G E N E R ATING SYSTEM OPERATION (400 AMPERE DUAL VOLTAGE AL
T E R N AT O R )
The 400-ampere dual voltage generating system maintains battery charge and provides electrical power to
operate vehicle circuits. Major components of the generating system are:
B
ALTERNATOR (400 AMPERE)
– Is rated at 28 volts at 400 amperes and 14 volts at 50 amperes
with external regulator. The alternator assists and recharges the vehicle batteries during operation.
A
BATTERY GAUGE
– Indicates electrical system voltage. It is connected to the electrical system
through circuit 567.
C
PROTECTIVE CONTROL BOX / DISTRIBUTION BOX*
– Protects the vehicle electric system in
the event battery polarity is reversed. Provides load dump, glow plug operation, and interfacing of
engine body harnesses.
D
CIRCUIT 2
– Sends AC signal, indicating alternator shaft rpm, to frequency switch in protective
control box to prevent operation of starter solenoid when engine is running.
E
BATTERIES
– Two 12-volt batteries are connected in a series to provide 24 volts to start vehicle and
assist alternator during operation.
G
POSITIVE CABLE 6
– Provides 28-volt alternator output to maintain charge across two batteries.
H
CIRCUIT 3
– Connects to negative stud on alternator with engine ground strap to provide a ground
circuit to alternator.
F
POSITIVE CABLE 68A
– Provides 16-volt alternator output to maintain charge across the lower
battery.
CIRCUIT 568
– Senses vehicle voltage, and activates the field current in the alternator circuit to
alternator.
I
*
Distribution box provides same function as protective control box except distribution box does not
protect against reversal of battery polarity.
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