TRAILER SERVICE BRAKES DO NOT FUNCTION (CAB GUARD) (Cont)

TM 9-2320-285-24-2

3-21. TREADLE VALVE AND BRAKE CONTROLS TROUBLESHOOTING (CONT)

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

11. TRAILER SERVICE BRAKES DO NOT FUNCTION (CAB GUARD) (Cont)

Step 2.

Relieve air system of all pressure (para 2-41h(1)).

Disconnect air hose connecting brake treadle valve to double check valve (located at bottom of

tractor protection valve).

Start tractor and allow air system to build to 100 psi pressure.

Push down trailer hand brake control valve fully.

Check for air exhaust at open port of double check valve.

a. If air is exhausting from double check valve, replace (para 3-24d).

b. If air is not exhausting from double check valve, proceed to step 3 below.

Step 3.

Relieve air system of all pressure (para 2-41h(1)).

Disconnect hose connecting trailer hand brake control valve to double check valve (located at

bottom of tractor protection valve).

Install calibrated air pressure gage on hose.

Start the tractor and allow air system to build to 100 psi pressure.

Push down trailer hand brake control valve fully.

Watch test gage.

Test gage shall indicate air system pressure (same as AIR PRESS gage indication).

a. If test gage indication is within 10 psi of AIR PRESS gage indication, proceed to step 4 below.

b. If test gage indication differs from AIR PRESS gage indication by more than 10 psi, replace

trailer hand brake control valve (para 3-24c).

Step 4.

Relieve air system of all pressure (para 2-41h(1)).

Disconnect hose connecting trailer hand brake control valve to double check valve (located at

bottom of tractor protection valve).

Start the tractor and allow air system to build to 100 psi pressure.

Depress brake treadle valve.

Check for air exhaust at open port of double check valve.

a. If air is exhausting from double check valve, replace (para 3-24d).

b. If air is not exhausting from double check valve, repair or replace tractor protection valve (para 3-

24h).

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