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 37 of 926
TM 9-2320-283-20-1
PRINCIPLES OF OPERATION.
1-11.
ENGINE (Continued).
c.
Engine Retarder Brake Controls.
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
power to
relay (RY-9), which
in turn provides 12-volt power to electrical system,
including engine retarder brake circuit.
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-2).
Protects electrical
components of
engine retarder brake circuit by opening when load
exceeds 20 amperes.
May be manually reset by pressing CB-2 button in.
FOOT SWITCH.
Allows driver to activate engine brake circuit with left foot. When depressed, switch supplies 12-volt
power through CB-2, throttle switch, and engine retarder switch, to energize selected solenoid valve(s).
THROTTLE SWITCH.
Switch is
open when accelerator pedal is
pressed down to prevent
activation of
engine retarder
brake.
Activating arm
on fuel pump lever closes switch when accelerator is disengaged.
ENGINE RETARDER SWITCH.
Three-position switch allows driver to select engine braking for two cylinders (LOW), four
cylinders (MED), or six cylinders (HIGH).
Depressing pedal actuated foot switch completes 12-volt power circuit to
energize one, two, or three solenoids.
SOLENOID VALVES.
Operate engine braking mechanism when activated.
TA 2366757
1-17
Back to Top
