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 54 of 926
TM 9-2320-283-20-1
PRINCIPLES OF OPERATION.
1-15.
ELECTRICAL SYSTEM (Continued).
c.
Service Lighting System (Continued).
(1) Headlamps and Taillamps.
When headlamp switch is in ON position and blackout toggle switch is in NORMAL position, battery power is supplied to
illuminate headlamps, tail- lamps, and trailer taillamps.
The trailer taillamps are powered through cab and chassis
connectors.
HIGH BEAM LAMP.
When power is supplied to each high
beam filament in the headlamps, the high beam indicator is
illuminated by the same circuit.
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.
CIRCUIT BREAKER (CB-9).
Protects 24-volt blackout stop, marker, and tail lamp circuits for trailers used with the
M915A1.
HEADLAMP SWITCH.
Has one OFF position and two ON
positions.
In either ON position,
12-volt battery power
illuminates taillamps.
Only when
pulled fully ON will headlamps illuminate.
DIMMER
SWITCH.
Two-position,
floor-mounted
switch.
Switch
is always closed in one of two positions to energize
either low beam or high beam headlamp filament.
BLACKOUT TOGGLE SWITCH.
Two-position safety switch for NORMAL and BLACKOUT modes of operation.
To select
mode, switch is pulled out and placed
to either
position.
Set to
NORMAL position,
12-volt power from
headlamp switch
passes through blackout toggle switch contacts to energize tail- lamps,
headlamps (through
dimmer
switch), and
coil of
relay.
Set
to
BLACKOUT position 12-volt power is removed from regular service lamps and electrical horn while 12-volt power from
headlamp switch is supplied through blackout toggle switch to blackout taillamp, marker lamps, and headlamps.
HEADLAMPS.
12-volt, dual filament, sealed beams.
TAILLAMPS.
Each assembly
contains two bulbs:
a double-element
bulb is used for taillamp, turn signal lamp, and
stoplamp; and a separate bulb is used for
the backup lamp.
The taillamp
circuit is energized through the blackout toggle
switch when headlamp switch is in either ON position.
RELAY
(RY-6).
When normally
open contacts
are
closed, relay
provides 24-volt power to trailer taillamps.
1-34
Back to Top
