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 99 of 926
TM 9-2320-283-20-1
PRINCIPLES OF OPERATION.
1-20.
BRAKE SYSTEM (Continued).
c.
Brake System Switches and Lamps.
BATTERY PACK.
Consists of four, 12-volt, maintenance free batteries.
Two batteries are wired in parallel in each set.
Each set is connected in series for 24-volt output.
Battery pack is used for both 12-volt and 24-volt output.
IGNITION SWITCH.
Supplies 24-volt to relay (RY-9), which in turn provides 12-volt power to electrical system, including
brake system switch and indicator circuits.
RELAY (RY-9).
Energized by 24-volt power from ignition switch.
When energized, RY-9 supplies 12-volt power to circuit
breaker (CB-2).
CIRCUIT BREAKER (CB-1).
Protects electrical components of stoplamp circuit by opening when load exceeds 20
amperes.
May be manually reset by pressing CB-1 button in.
CIRCUIT BREAKER (CB-2).
Protects electrical components of stoplamp circuit by opening when load exceeds 20
amperes.
May be manually reset by pressing CB-2 button in.
CIRCUIT BREAKER (CB-8).
Protects electrical components of 24-volt trailer brake system relay circuit by opening when
load exceeds 20 amperes.
May be manually reset by pressing CB-8 button in.
CIRCUIT BREAKER (CB-9).
Protects electrical components of 24-volt trailer brake system relay circuit by opening when
load exceeds 20 amperes.
May be manually reset by pressing CB-9 button in.
PARK BRAKE LAMP.
Illuminates when park brakes are applied.
Receives 12-volt power through circuit breaker CB-2
when parking brake switch is closed.
PARK BRAKE SWITCH.
Normally open, air actuated switch, located on parking brake.
Closes to energize park brake
lamp when parking brakes are actuated.
STOPLAMP SWITCH.
Normally open air actuated switch.
Closes when brakes are actuated.
Receives 12-volt power
from circuit breaker CB-1 and supplies this power to blackout toggle switch.
BLACKOUT TOGGLE SWITCH.
Two-position switch for NORMAL and BLACKOUT modes of operation.
12-volt power is
received from closed stoplamp switch and circuit breaker CB-1.
With switch set to NORMAL position, 12-volt power is
supplied through turn signal switch to tractor taillamps-stoplamps.
Also, 12-volt power is supplied to 12-volt trailer
connector.
With switch set to BLACKOUT position, 12-volt power is supplied to blackout stoplamps.
1-78
Back to Top
