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)

CHECKLIST 4

If there is excessive leakage in the service side of the pneumatic system, one or more of the following devices could be causing the

problem:

NOTE: A leak detector or soap solution will aid in locating the faulty component.

1. Loose service lines and ﬁ ttings

2. Stoplight switch

3. Trailer control valve

4. Dual brake valve

5. Tractor protection valve

6. Double check valve

7. Service brake relay valves

8. Spring brake chamber, service chamber and/or brake chamber diaphragms

9. Inverting relay spring brake control valve (where applicable – usually found on the spring brake relay valve) straight trucks and buses

If the automatic slack adjuster is not adjusting, repair or replace to obtain desired setting.

CAUTION: If the brake chamber push rod travel exceeds the allowable stroke, identify and correct the root cause of the excess stroke. Do

not make manual adjustments of an automatic slack adjuster once it can no longer automatically adjust the brakes. Manual adjustment

DOES NOT ﬁ x the underlying wheel end adjustment. As soon as possible, have the vehicle inspected by a qualiﬁ ed technician or consult

the manufacturer’s troubleshooting guidelines to ﬁ nd and ﬁ x the problem.

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

TEST 5

MANUAL PARKING BRAKE OPERATION

FULL PRESSURE, ENGINE IDLING 600-900 RPM

;

Not

FOR STRAIGHT TRUCKS, BUSES AND BOBTAIL TRACTORS:

1. Manually operate the park control, yellow button valve, and note that the parking brakes apply and release promptly as the

control valve button is pulled out and pushed in.

FOR TRACTOR/TRAILER COMBINATIONS:

1. Manually operate the tractor protection control valve (trailer supply valve usually red octagonal button). Note that the trailer

brakes apply and release promptly as the control button is pulled out and pushed in.

2. Manually operate system park control (usually yellow diamond button) and note that all parking brakes (tractor and trailer)

apply promptly.

MAKE ALL NECESSARY REPAIRS BEFORE PROCEEDING TO TEST 6;

SEE CHECKLIST 5 FOR COMMON CORRECTIONS.