TM-9-2320-283-20-1
TRUCK TRACTOR, LINE HAUL, 50,000 GVWR, 6X4, M915A1
TECHNICAL MANUAL; ORGANIZATIONAL MAINTENANCE PART 1 OF 3
DECEMBER 1983
TM-9-2320-283-20-1 - Page 66 of 926
TM 9-2320-283-20-1
PRINCIPLES OF OPERATION.
1-15.
ELECTRICAL SYSTEM (Continued).
c.
Service Lighting System (Continued).
(5)
Instruments, Gages, Dome Lamp, and Map Lamps.
RELAY (RY-8).
Normally closed contacts are opened by 12-volt
power when blackout toggle switch is placed in
BLACKOUT position.
This prevents the dome and map lamps from coming on whenever the blackout toggle switch is in
the BLACKOUT mode.
BLACKOUT TOGGLE SWITCH.
Two-position switch for NORMAL and BLACKOUT modes of operation.
In this circuit,
the switch is used to prevent operation of the dome and map lamps.
In BLACKOUT
position, 12-volt power from circuit
breaker CB-1 passes through the switch and energizes coil of relay RY-8,
thus preventing dome and map lamps from
possibly coming on.
DOME LAMP
AND MAP LAMPS SWITCH ASSEMBLY.
When the dome lamp or map lamps switch is in ON position and
the blackout toggle switch is in NORMAL position, the lamp is energized by 12-volt power through relay (RY-8) and circuit
breaker (CB-1).
HEADLAMP SWITCH.
Has one OFF position and two ON positions.
In either ON position, 12-volt power passes through
the switch to energize the following lamps in this circuit:
(a)
Instrument lamps on left-hand instrument cluster.
(b)
Clearance, ether switch, and tachograph illumination lamps on center cluster.
(c)
Switch and functional indicators on right-hand instrument cluster.
(d)
Illumination lamps on heater panel.
(e)
Illumination lamps on shifter control tower.
The headlamp switch has a variable rheostat that allows the operator to adjust the brightness of all lamps in this circuit by
turning the switch knob.
TACHOGRAPH.
Receives 12-volt power from headlamp switch for illumination.
WINDSHIELD WIPER
AND WASHER LAMPS.
Receives 12-volt power from headlamp switch for illumination.
HEATER PANEL LAMPS.
When headlamp switch is in either ON position, lamps are energized by 12-volt power and
illuminate heater control panel.
TRANSMISSION
SHIFTER CONTROL LAMP.
When headlamp
switch is in either ON position, lamp is energized by 12-
volt battery power and illuminates transmission shifter control.
1-46
Back to Top
