Truck Troubleshooting Guide - WABCO

1 472 500 30. 0 MADE IN GERMANY001 20/98xxxxxxxxxxxxxxx xxxxxxxxxx xxxxxxxxxx xxxxx20A20B61 COLOR KEYSUPPLYSECONDARYPRIMARYPARK/EMERGENCYA BS ELECTRICAL152013205725549382910201213201 9211201213201718B20131416152018A16 SECONDARYCONTROLTO SERVICERELAYPRIMARYTANKFROM PARKVALVEINSET (A) OPTIONPRIOR TO MARCH 1, 1998 FMVSS-121 REGULATIONSINVERSION VALVE AND QUICK RELEASE VALVE(INCLUDES ANTI-COMPOUNDING)INSET (A)SECONDARYPRIMARYSUPPLY(WET TANK)ECUISSUED 10/99 TP-9974 Truck Troubleshooting GuideCONDITION/REMEDYCONDITION/REMEDYCON DITION/REMEDYCONDITION/REMEDYM eritor WABCO Vehicle Control Systems2135 West Maple RoadTroy, MI 48084-7121 contained in this publication was in effect at the time the publication was approved for printing and is subject tochange without notice or liability.

2 Meritor WABCO reserves the right to revise the information presented or to discontinue theproduction of parts described at any 1999 ArvinMeritor, Rights ReservedPrinted in USATP-9974 Issued 10-9916579/22882 Truck Troubleshooting GuideFRONT AXLE VALVE PACKAGE(OPTIONAL)COMBINES TWO MODULATOR VALVES AND QUICKRELEASE AXLE VALVE PACKAGE(OPTIONAL)COMBINES TWO MODULATOR VALVES AND : If the vehicle has Meritor WABCO ABS, refer to MeritorWABCO Maintenance Manual 28 (C version ABS) or 30(D version ABS).COMPRESSORFOR Troubleshooting INFORMATION REFER TO THE OEMOPERATING : If the compressor is manufactured by Meritor WABCO ,refer to Maintenance Manual 31 (318 Compressor for MackE Tech Engines) or contact the Meritor Customer SupportCenter at , PRIMARY AND SECONDARY AIRTANKSFOR Troubleshooting INFORMATION REFER TO THE OEMOPERATING PRESSURE INDICATOR SWITCHBUZZER OR LIGHT INOPERABLEC heck ground and wiring on switch and switch or T OPERATE AT PRESSURES BELOW 60 dash gauge for switch or VALVE POPS OFF EXCESSIVELYC heck system operating properly when venting at 140/150 (as required).

3 Check unloader/governor. POPS OFF AT LESS THAN 140 T FUNCTIONP eriodic Test: remove and test above 150 with shop if VALVES - VALVES - AUTOMATICWON T DRAINR epair or T DRAIN IN COLD WEATHERR eplace with heated - MALFUNCTIONSR epair or Test: with system pressure stabilized (compressorunloaded) no leak evident at discharge port - make several footbrake applications to reduce wet tank pressure. Moistureshould drain from discharge unloader line size (5/16 x 5 maximum).Check air actuated accessory. Is the air volume requirementgreater than governor capacity?Check for plugged governor reservoir , adjust or replace T PASS AIR TO UNLOADER TO CUT-OUT COMPRESSORC heck governor reservoir or CHECK VALVEALLOW BLEED BACK TO SUPPLY RESERVOIRP eriodic Test.

4 Bleed supply reservoir and observe valves should maintain primary and secondary if test results are CONTROL CHECK VALVEWILL NOT PERMIT AIR TO PURGE AIR THAT ONE-WAY CHECK HAS BEEN GAUGEFOR Troubleshooting INFORMATION REFER TO THE OEMOPERATING SYSTEM FOOT BRAKE VALVELEAKS AT EXHAUST WITH ALL BRAKES RELEASEDC heck anti-compound double check valve # #18A & 18B for back flow into service control seal in spring brake for back-flow of spring hold-off pressure through service port to open exhaust on #15 Spring Parking : CHOCK WHEELS - REPAIR AND REPLACE ITEMS AT EXHAUST WITH FOOT BRAKE APPLIEDFoot valve defective.

5 Repair or AT EXHAUST WITH ALL PARK BRAKES SET IN PARKPOSITION AND FOOT BRAKE RELEASEDFoot valve defective. Repair or RELEASE VALVELEAKS AT EXHAUST PORT WITH ALL BRAKES RELEASEDC heck and replace #18A or 18B if back flow occurs intosecondary control WHEN SERVICE BRAKES ARE APPLIEDR epair or BRAKE CHAMBERFOR Troubleshooting INFORMATION REFER TO THE OEMOPERATING ADJUSTERFOR Troubleshooting INFORMATION REFER TO THE OEMOPERATING : If the slack adjusters are manufactured by Meritor, referto Maintenance Manual 4B (Automatic Slack Adjusters) orcontact the Meritor Customer Support Center at 800-535-5560(Ilamasin costo desde Mexico 001-800-889-1834).

6 RELAY VALVELEAKS AT EXHAUST PORT WITH ALL BRAKES RELEASEDC heck seal in spring brake for back-flow of spring hold-off pressure through service port to open exhaust on #15 Spring Parking reservoir port for evidence of contamination, checksupply lines for rusty fittings or carbon deposits. Repair AT EXHAUST PORT WITH SERVICE BRAKES APPLIEDE xhaust valve not seating properly. Repair or PARKING BRAKE(SERVICE ONLY SERVICE CHAMBER SIDEOF SPRING BRAKE)FOR Troubleshooting INFORMATION REFER TO THE OEMOPERATING RELEASE AND DOUBLE CHECKVALVE COMBINATIONFOOT VALVE EXHAUST LEAK PARK BRAKES RELEASED YELLOWDASH CONTROL V VALVE EXHAUST LEAK IN PARK POSITIONAND SERVICE BRAKES APPLIEDC heck anti-compound double check valve portion for feedbackto foot or dash control valve.

7 Repair or LIGHT TO SIGNAL A GOOD BULB THROUGH SOUND WIRING AT3-6 RELAY VALVE WITH THE LOSSOF REAR SERVICE BRAKES,APPLICATION OF SPRING BRAKE BYUSING THE EMERGENCY SECTIONSHOULD BE AVAILABLE ALONG WITHFRONT SERVICE BRAKE BY APPLYINGFOOT VALVEPERIODICALLY TEST BY BLEEDING PRIMARY SERVICE TANK ANDOBSERVING FRONT BRAKE AND REAR SPRING BRAKEAPPLICATION UPON DEPRESSING FOOT PEDAL. REPAIR ORREPLACE, IF AFTER CHECKING INVERSION VALVE IS NOTFUNCTIONING or DRYERAIR LEAKING CONSTANTLY FROM PURGE VALVEP urge valve seal damaged. valve heater (see heater problems).HEATER INOPERATIVEB lown Fuse. Check fuse and replace with 8-10 amp fuseBroken wires or poor connections.

8 Repair or replace wiring WET TANK BUILD-UPFilter and/or desiccant plugged. Service air a System Saver Series air dryer is installed, refer to MeritorWABCO Maintenance Manual 34 (Single Canister) or35 (TWIN).ABS ELECTRONIC CONTROL UNIT,MODULAR VALVES, SENSORS, ANDTOOTH RINGSFOR Troubleshooting INFORMATION REFER TO THE OEMOPERATING