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 72 of 926
TM 9-2320-283-20-1
PRINCIPLES OF OPERATION.
1-15.
ELECTRICAL SYSTEM (Continued).
e.
Relays, Circuit Breakers, and Diode.
RELAY (RY-1).
When normally open contacts are closed, relay provides 12-volt power to electric horn.
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.
RELAY (RY-5).
When normally open contacts are closed, relay provides 24-volt power to trailer blackout taillamps.
RELAY (RY-6).
When normally open contacts are closed, relay provides 24-volt power to trailer marker and taillamps.
RELAY (RY-7).
When normally closed contacts are opened, relay disconnects 12-volt power from tractor backup lamps.
RELAY (RY-8).
When normally closed contacts are opened, relay
disconnects 12-volt power from dome lamp and map
lamps.
RELAY (RY-9).
When normally open contacts are closed, relay provides 12-volt power to heater motor, backup lamp,
defroster fans, ether quick-start kit,
engine brake retarder, air dryer, low air switch, park brake switch, differential lockout
switch, instrument gages, and indicator lamps.
1-52
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