TM-9-2320-272-23-1
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; FIELD MAINTENANCE MANUAL; VOLUME 1 OF 5
SEPTEMBER 2012
TM-9-2320-272-23-1 - Page 233 of 1313
GENERATING SYSTEM OPERATION
The generating system is identical for all vehicles covered in this manual and consists of the following major
components and circuitry:
A. VOLTMETER
- Indicates electrical system voltage. It is connected to the electrical system through
circuit
27.
B. ALTERNATOR
- Rated at 26-30 volts, 60 amperes, the alternator assists and recharges batteries during
operation. A 100-ampere model is available as a kit.
C. CIRCUIT 3
- Provides a ground circuit to alternator.
D. CIRCUIT 566
- Controls a relay in protective control box that prevents starter from reactivating while
engine is running.
E. CIRCUIT 568
- Senses system voltage and excites the alternator field.
F. PROTECTIVE CONTROL BOX
- Connects circuit 5 to 80 to power the electrical system and charge
the
batteries.
G. CIRCUIT 5
- Conducts alternator output to charge batteries and maintain vehicle voltage.
H. BATTERY SWITCH
- Closes relay in protective control box that connects battery circuits.
B
C
D
E
F
G
5A
CB
5
568
3
566
459
81A
H
81
6
27
A
G0032DAA
BATTERY
STATER SOLENOID
BATTERY TERMINAL
Figure 20.
Generating System Components.
TM 9-2320-272-23-1
0003
0003-28
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