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 234 of 1313
DIRECTIONAL SIGNAL SYSTEM OPERATION
The directional signal system is identical on all models covered in this manual and consists of the following major
components and circuitry:
A. LIGHT SWITCH
- Provides battery power to directional signal switch through circuits 460 and 461 and
to stoplight switch through circuit 75.
B. STOPLIGHT SWITCH
- Closing this switch allows power to flow from light switch through circuit 75 to
circuit 22 to directional signal switch.
C. REAR COMPOSITE LAMPS
- Receive power from turn signal control through circuit 22-460 and 22-461
to indicate turning direction.
D. TURN SIGNAL FLASHER
- Receives power through circuit 467A and sends intermittent current to the
signal lamp through circuit 467B.
E. DIRECTIONAL SIGNAL SWITCH
- A four-position switch that directs power to composite and signal
lamps through circuits 460, 461, 22-460, and 22-461 to indicate direction of turn.
F. FRONT COMPOSITE LAMP
- Receives power from turn signal control through circuits 460 and 461 to
indicate turning direction.
C
C
B
A
F
F
E
D
22-461
57
467B
467A
461
460
22
460-461
22-460
75
75
15
G0033DAA
Figure 21.
Directional Signal System Components.
TM 9-2320-272-23-1
0003
0003-29
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