TM-9-2320-272-23-1
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; FIELD MAINTENANCE MANUAL; VOLUME 1 OF 5
SEPTEMBER 2012
TM-9-2320-272-23-1 - Page 1163 of 1313
FRONT WHEEL DRIVE DOES NOT ENGAGE (FRONT WHEEL DRIVE LOCK-IN SWITCH ENGAGED AND
TRANSFER CASE SHIFT LEVER IN HIGH POSITION) - Continued
STEP
7.
IS THERE AIR PRESSURE IN THE AIR LINE CONNECTED TO THE FRONT WHEEL DRIVE LOCK-IN
SWITCH?
a.
Stop engine.
b.
Disconnect pressure gauge from vehicle and return air line to original condition.
c.
Disconnect air line from front wheel drive lock-in switch. Refer to point to point schematics.
T0348DAA
AIR LINE
(TO
ACTUATOR
VALVE)
TRANSDUCER
FRONT WHEEL
DRIVE LOCK - IN
SWITCH
Figure 7.
Front Wheel Drive Lock-in Switch.
d.
Connect pressure gauge to front wheel drive lock-in switch.
e.
Start engine and run at idle.
f.
Place transfer case shift lever into high position.
g.
Engage front wheel drive lock-in switch.
h.
Monitor air pressure on pressure gauge.
i.
After 5 minutes air pressure should read 90 to 130 psi.
CONDITION/INDICATION
IS THERE AIR PRESSURE IN THE AIR LINE CONNECTED TO THE FRONT WHEEL DRIVE LOCK-IN
SWITCH?
DECISION
YES - Replace defective air line at the front wheel drive lock-in valve (Volume 5, WP
0805). Go to Step (10) to
verify problem is solved.
NO - Replace defective front wheel drive lock-in switch (Volume 3, WP
0389). Go to Step (10) to verify problem
is solved.
TM 9-2320-272-23-1
0140
0140-8
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