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 255 of 481

TM 9-2320-272-10

2-154

2-26. OPERATION OF TRACTOR AND FIFTH WHEEL (Contd)

(9)

Press in trailer air supply

valve (3) and hold in place for 15 seconds.

Release valve (3). Valve (3) should remain

in engaged position indicating semitrailer

airbrake system has proper air pressure.

If valve (3) does not remain in engaged

position, disconnect couplings (9) and

notify your supervisor.

(10)

Pull down trailer air

brake hand control lever (2) to engage

semitrailer brakes.

.

WARNING

.

Do not back up without a ground guide. Doing so may result in

damage to vehicle, injury, or death.

(11)

Release parking brake lever (6), place transmission selector lever (5)

in R (reverse), and resume backing up.

(12)

Stop vehicle when coupling jaws (7) close around semitrailer

kingpin (8). Visually check to make sure jaws (7) have completely closed.

(13)

With trailer air brake control handle (2) engaged, place

transmission selector lever (5) in 1 (first) and slightly depress accelerator pedal.

Tractor will not move forward if fifth wheel is properly connected to semitrailer.

CAUTION

Stop vehicle immediately if tractor moves forward and repeat

task c, steps 9 through 12.

(14)

Place transmission selector lever (5) in N (neutral) and apply

parking brake lever (6).

(15)

Connect electrical cable (11) to electric receptacle (10) on semitrailer.