TM-9-2320-272-10
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; OPERATOR'S MANUAL
SEPTEMBER 2004
CHANGE 2
TM-9-2320-272-10 - Page 86 of 481
TM 9-2320-272-10
1-69
1-20. COMPRESSED AIR AND BRAKE SYSTEM OPERATION (Contd)
J
FRONT AXLE ENGAGEMENT CONTROL VALVE
– Operates off cam on
transfer case shift linkage so front-wheel drive engages automatically when
transfer case is put into LOW.
H
GOVERNOR
– Serves as a tee between accessory manifold and horn relay
valve. It also signals the air compressor to stop compressing air for the supply
system when operating pressure has been reached.
I
TRANSFER CASE AIR SHIFT CYLINDER
– Engages front-wheel drive
when it receives air pressure from lock-in switch or engagement control
valve.
K
HORN RELAY VALVE
– Electrical signal from horn button on steering
wheel opens valve in horn relay, allowing air pressure to sound horns.
E
ACCESSORY MANIFOLD
– Receives air pressure from the pressure
protection valve and distributes it to the various accessories.
A
WINDSHIELD WIPER CONTROL SWITCH
– Opens air pressure valve in
wiper motor to operate wipers.
B
WINDSHIELD WIPER MOTOR
– Air-actuated motor powers windshield
wipers.
D
WINDSHIELD WASHER RESERVOIR
– Container for windshield washer
fluid.
G
WINDSHIELD WASHER NOZZLES
– Direct washer fluid on windshield.
L
HORNS
– Receive air pressure from horn relay valve to sound off.
F
FRONT-WHEEL DRIVE LOCK-IN SWITCH
– Air-actuated switch that
engages front-wheel drive when transfer case is in HIGH.
C
WINDSHIELD WASHER CONTROL
– Spring-loaded valve that allows air
pressure to force washer fluid from washer reservoir to windshield.
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