TM-9-2320-272-24-1

TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)

TECHNICAL MANUAL; UNIT, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE MANUAL; VOLUME 1 OF 4

JUNE 1998

TM-9-2320-272-24-1 - Page 274 of 1015

TM 9-2320-272-24-1

Table 2-4. Compressed Air and Brake System Troubleshooting (Contd).

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

Test 9. Test doublecheck valve No. 1(2) supply pressure (front service brake chambers test low or

nonexistent air pressure).

WARNING

Do not depress service brake pedal during installation of test

gauge. This may result in injury to personnel.

Step 1.

Direct assistant to keep foot off service brake pedal (6).

Step 2.

Disconnect air supply line (1) from doublecheck valve No. 1 (2).

Step 3.

Connect test gauge to air supply line (1). Direct assistant to start engine and allow air

pressure to build to normal operating pressure.

Step 4.

Depress service brake pedal (6).

Step 5.

Check reading on test gauge.

a.

If pressure reads normal and delivery line (3) is not blocked (as determined by

test 8), replace defective doublecheck valve No. 1 (2) (para. 3-212).

b.

If pressure is below normal or nonexistent, stop engine, drain air, remove test gauge,

connect delivery line (3), and perform test 10.

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