MWO-9-2320-272-35-1
MODIFICATION OF 5-TON M939, M939A1, M939A2 SERIES FAMILY OF VEHICLES (FOV)
M939 BRAKE STABILIZATION PROGRAM (RETROFIT OF ANTI-LOCK BRAKE SYSTEM (ABS) FOR M939 FOV); MODIFICATION WORK ORDER
JANUARY 2007
CHANGE 1
MWO-9-2320-272-35-1 - Page 26 of 109
MWO 9-2320-272-35-1
24
g. Air Dryer Electrical Check
Turn battery switch to ON position and starter switch to RUN position. Disconnect air dryer harness
connector and check voltage between two pins in vehicle harness connector. The voltage should be
approximately 24-volts.
h. Check Valves Test
(1)
Verify operation of check valves by draining secondary reservoir.
(a) Primary reservoir pressure should NOT decrease when secondary reservoir is being
drained, however a 10-15 psi decrease is allowable.
(b) If primary reservoir pressure does decrease along with secondary, inspect and clean or
replace the primary reservoir one-way check valve or doublecheck valve No. 7 as needed.
(2)
Start engine and allow air pressure to build to normal operating pressure (TM 9-2320-272-10).
(3)
Shut engine down (TM 9-2320-272-10.)
(4)
Verify operation of check valves by draining primary reservoir.
(a) Secondary reservoir pressure should NOT decrease as primary reservoir is being drained,
however a 10-15 psi decrease is allowable.
(b) If secondary reservoir pressure does decrease along with primary, inspect and clean or
replace the secondary reservoir one-way check valve or doublecheck valve No. 7 as needed.
(5)
While rotating rear wheels, validate inversion valve operation by verifying spring brakes
engage when brake pedal is depressed. With primary air tank drained, spring brake dust
cover removed for visual access, and spring brake override disengaged, diaphragm in spring
brake chamber should compress and release as foot valve is operated (TM 9-2320-272-10).
(6)
Install rear-rear axle shafts (TM 9-2320-272-24).
NOTE
NOTE
Ensure all inspections, except inspection “l”, on the Quality
Assurance Checklist (appendix A) are performed prior to
performing step 7.
(7)
Raise vehicle, remove jackstands, and lower vehicle to ground (TM 9-2320-272-24).
i.
Road Test
(1)
With Haldex Info-Centre still connected to diagnostic connector, drive vehicle above 6 miles
per hour.
(a) The ABS indicator lamp should remain OFF.
(b) The Haldex Info-Centre display code should change from 07 to 00 and sensor indicator
bars on each side of -00- should be displayed.
(2)
Make one quick, hard stop from 25 miles per hour or less to initiate ABS.
(a) Verify ABS indicator lamp remains OFF. If lamp illuminates or codes other than 07 are
displayed, refer to diagnostics and troubleshooting (step j) to correct problem.
(b) If no fault codes appear and ABS indicator lamp remains OFF, antilock brake system is
operating properly.
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