Troubleshooting guide

For more information, visit www.bendix.com or www.foundationbrakes.com • 1-800-AIR-BRAKE (1-800-247-2725)

Air Brake System Troubleshooting Tests (continued)

Dual circuit system integrity check (emergency braking) and/or automatic

application of the parking brake and/or Tractor protection valve operation

FULL PRESSURE, ENGINE STOPPED, PARKING BRAKES RELEASED

;

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4. For Towing Vehicles Only - Test the tractor protection valve feature

A. Charge the air system to governor cut-out.

B. Disconnect the service or control (blue) line to the trailer.

C. Take care to restrain the service coupling and direct ﬂ ow safely away while making and holding a full service brake

application via the foot valve.

D. As the service application is vented through the open gladhand, the service system pressure drops until the tractor

protection control (red) valve trips and shuts off the leak through the open coupling. This leak must be shut off.

E. Record the pressure in the service reservoirs. Disconnect the trailer supply coupling to verify that the supply or emergency

(red) coupling has been vented to atmosphere, thereby activating the trailer emergency feature.

5. Close the drain cocks, recharge the system and drain the rear axle primary reservoir to 0 psi.

A. The front axle reservoir should retain most of its pressure.

B. On combination vehicles, the trailer air system should remain charged.

6. With no air pressure in the rear axle reservoir, make and release a brake application.

A. Front axle brakes should apply and release.

B. On combination vehicles, the trailer brakes should also apply and release.

C. If the vehicle is equipped with a spring brake modulating valve, typically found on trucks, towing trucks and buses, the rear

axle brakes should also apply and release by exhausting spring brake air.

MAKE ALL NECESSARY REPAIRS BEFORE PROCEEDING;

SEE CHECKLIST 6 FOR COMMON CORRECTIONS.

CHECKLIST 6

If the vehicle fails to pass the tests outlined, then check the following components for leakage and proper operation:

1. Fittings 2. Kinked hose or tubing

3. Pressure protection valves 4. Double check valves

5. Tractor protection valve 6. Tractor protection control valve

7. Parking control valve 8. Relay valves (antilock modulators)

9. Trailer spring brake control valve 10. Inverting relay spring brake control valve

(optional) straight trucks and buses

TEST 6 (Continued)

RETEST TO VERIFY PROPER OPERATION OF ALL ITEMS REPAIRED OR REPLACED.