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 101 of 926
TM 9-2320-283-20-1
PRINCIPLES OF OPERATION.
1-20.
BRAKE SYSTEM (Continued).
c.
Brake System Switches and Lamps (Continued).
TAILLAMPS-STOPLAMPS.
Each assembly contains two bulbs:
a single-filament bulb for the backup lamp; and a two-
filament bulb for the taillamp, turn signal lamp, and stoplamp.
Receive 12-volt power through circuit breaker CB-1, closed
stoplamp switch, closed contacts of blackout toggle switch, and turn signal switch.
12-VOLT TRAILER CONNECTOR.
When stoplamp switch is closed and blackout toggle switch is in NORMAL position,
12-volt power is supplied to tractor mounted connector for trailer stoplamps.
REAR AIR PRESSURE GAGE.
Direct pressure gage indicates air pressure in rear service reservoir.
LOW AIR PRESSURE WARNING
INDICATOR (12-volt).
Circuit normally held open by air pressure.
Closes to activate control panel indicator when
pressure drops below 70 psi.
FRONT AIR PRESSURE GAGE.
Direct pressure gage.
Indicates air pressure in front service reservoir.
24-VOLT TRAILER CONNECTOR.
Cab mounted 12-pin connector to provide 24-volt power to trailers.
24-VOLT TRAILER CONNECTOR.
Chassis mounted 12-pin connector to provide 24-volt power to trailer stoplamps.
RELAY (RY-2).
When normally open contacts are closed, relay provides 24-volt power to trailer left turn signal lamp.
RELAY (RY-3).
When normally open contacts are closed, relay provides 24-volt power to trailer right turn signal lamp.
RELAY (RY-4).
When normally open contacts are closed, relay provides 24-volt power to trailer blackout stoplamp.
TURN SIGNAL CONTROL.
Receives 12-volt power from blackout toggle switch and distributes 12-volt power to right and
left taillamps-stoplamps, 12-volt trailer connector, and relay (RY-3).
1-80
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