TM-9-2320-272-24-1
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; UNIT, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE MANUAL; VOLUME 1 OF 4
JUNE 1998
TM-9-2320-272-24-1 - Page 60 of 1015
TM 9-2320-272-24-1
1-22. ELECTRICAL SYSTEMS OPERATION (Contd)
e. 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:
Key Item and Function
1
2
3
4
5
6
FRONT COMPOSITE LAMP
- Receives power from turn signal control through circuits 460 and
461 to indicate turning direction.
LIGHT SWITCH
- Provides battery power to directional signal switch through circuits 460 and 461
and to stoplight switch through circuit 75.
STOPLIGHT SWITCH
- Closing this switch allows power to flow from light switch through circuit
75 to circuit 22 to directional signal switch.
REAR COMPOSITE LAMPS
- Receive power from turn signal control through circuit 22-460 and
22-461 to indicate turning direction.
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.
TURN SIGNAL FLASHER
- Receives power through circuit 467A and sends intermittent current
to the signal lamp through circuit 467B.
1-50
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