Tractor Troubleshooting Guide - Meritor WABCO

1 Tractor Troubleshooting Guide ISSUED 10/99 TP-9973472 500 30. 0 MADE IN GERMANY001 20/98xxxxx xxxxxxxxxx xxxxxxxxxx xxxxxxxxxx xxxxx16 COLOR KEYSUPPLYSECONDARYPRIMARYPARK/EMERGENCYA BS ELECTRICALTRAILER CONTROLTRAILER SUPPLY1520132057255493829106120121320192 112012132020131416152018A16 SECONDARYCONTROLPRIMARYTANKFROM PARKVALVEINSET (A) OPTIONPRIOR TO MARCH 1, 1998 FMVSS-121 REGULATIONSINVERSION VALVE AND QUICK RELEASE VALVE(INCLUDES ANTI-COMPOUNDING)SECONDARYPRIMARYSUPPLY( WET TANK)ECU18 BSECONDARYCONTROLTO SERVICERELAYFROM PARKVALVEINSET (B) OPTIONAFTER MARCH 1, 1998 FMVSS-121 REGULATIONSNEW INVERSION VALVE AND QUICK RELEASE VALVE(INCLUDES ANTI-COMPOUNDING)PRIMARYDELIVERY22232417 212525 SIDE VIEWINSET (A) OR (B)20A20 BTO SERVICERELAYCONDITION/REMEDYCONDITION/RE MEDYCONDITION/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 to change withoutnotice or liability.

2 Meritor WABCO reserves the right to revise the information presented or to discontinue the production of parts describedat any time. Copyright 1999 ArvinMeritor, Inc. All Rights ReservedPrinted in USATP-9973 Issued 10-9916579/22882 Tractor Troubleshooting GuideHAND CONTROL VALVE-TRAILER SERVICEBRAKES LEAKS AT EXHAUST PORT WHEN RELEASED AND FOOT VALVEIS APPLIED Check #23. Replace if necessary. LEAKS AT EXHAUST PORT WHEN RELEASED AND TRAILERPARKING BRAKES ALSO RELEASED Check #21 for internal backflow into service control line, ortrailer air system for backflow into Tractor service control line. LEAKS AT EXHAUST PORT WHEN RELEASED OR APPLIED ANDALL PARKING BRAKES IN PARKED POSITION Hand control valve is defective. Repair or CHECK VALVE SEPARATESTRAILER HAND VALVE PRESSURE FROMREAR FOOT BRAKE PRESSURE FORDELIVERY TO TRAILER FOOT VALVE EXHAUST PORT LEAKS WHEN HAND VALVE ISAPPLIED Replace. HAND VALVE EXHAUST PORT LEAKS WHEN FOOT VALVE ISAPPLIED CHECK VALVE SEPARATESFRONT AXLE FOOT BRAKE PRESSUREFROM REAR AXLE FOOT BRAKEPRESSURE AND/OR TRAILER HANDVALVE PRESSURE FOR DELIVERY TOTRAILER LEAKS THROUGH FOOT VALVE EXHAUST WITH HAND VALVEAPPLIED Replace #23 or #24.

3 Periodic Test: Alternately loosen each inlet line and applypressure to other. If leak is detected - DASH VALVE WITH BUILT-INTWO-WAY CHECK (RED OCTAGON)TRAILER CHARGE (YELLOW DIAMOND) Tractor PARK PARK BRAKE WON T RELEASE Check for full system pressure delivery through valve. PARK BRAKE WON T APPLY Repair or replace, if it will not release pressure. LEAKS AT EXHAUST PORT IN PARK POSITION AND SERVICEBRAKES APPLIED Check #16 anti-compound double check valve. LEAKS AT EXHAUST PORT IN PARK POSITION AND SERVICEBRAKES RELEASED Repair or replace. WON T APPLY TRAILER IMMEDIATELY WHEN PULLED Replace, if it won t exhaust. Repair or replace #21 if #25 isfunctioning properly. PRIMARY TANK BLEED-DOWN ALSO BLEEDS SECONDARY TANKOR VICE VERSA Periodic Test: Pressure should remain in one tank after theother is drained. Replace, if Manual 28 (C version ABS) or 30 (D version ABS).TWO-LINE Tractor PROTECTION VALVE(NON-AUTOMATIC TYPE) WILL NOT RESPOND TO TRAILER CHARGE VALVE Defective valve.

4 Repair or replace. SUPPLY LINE TO TRAILER WITH SLOW BLEED-DOWN DOES NOTSHUT OFF Tractor AIR AND VENT BETWEEN 45 AND20 Check trailer charge valve #25, as it should pop to let vent trailer supply. Repair or replace. LEAKS AT EXHAUST PORT OR Tractor SERVICE (BACKTHROUGH HAND OR FOOT VALVE) OR TRAILER SUPPLY Defective valve. Repair or replace. FOR Troubleshooting INFORMATION REFER TO THEOEM OPERATING 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 Meritor WABCOCOMPRESSOR FOR Troubleshooting INFORMATION REFER TO THE OEMOPERATING INSTRUCTIONS. NOTE: 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 AIRTANKS FOR Troubleshooting INFORMATION REFER TO THE OEMOPERATING PRESSURE INDICATOR SWITCH BUZZER OR LIGHT INOPERABLE Check ground and wiring on switch and buzzer/light.

5 Replace switch or buzzer/light. WON T OPERATE AT PRESSURES BELOW 60 Check dash gauge for accuracy. Replace switch or VALVE POPS OFF EXCESSIVELY Check system pressure. Valve operating properly when venting at 140/150 (as required). Check unloader/governor. POPS OFF AT LESS THAN 140 Replace. LEAKS Replace. WON T FUNCTION Periodic Test: remove and test above 150 with shop air. Replace if VALVES - MANUAL LEAKS VALVES - AUTOMATIC WON T DRAIN Repair or replace. WON T DRAIN IN COLD WEATHER Replace with heated unit. LEAKS - MALFUNCTIONS Repair or replace. Periodic Test: with system pressure stabilized (compressorunloaded) no leak evident at discharge port - make severalfoot brake applications to reduce wet tank pressure. Moistureshould drain from discharge FLUTTERS Check gauge. Check 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 line.

6 Repair, adjust or replace governor. WON T PASS AIR TO UNLOADER TO CUT-OUT COMPRESSOR Check governor reservoir line. Repair or CHECK VALVE ALLOW BLEED BACK TO SUPPLY RESERVOIR Periodic Test: bleed supply reservoir and observe valves should maintain primary and secondary reservoirpressure. Replace if test results are CONTROL CHECK VALVE WILL NOT PERMIT AIRFLOW REQUIRED TO PURGE AIR DRYER Make sure the single check valve has been GAUGE FOR Troubleshooting INFORMATION REFER TO THE OEMOPERATING SYSTEM FOOT BRAKE VALVE LEAKS AT EXHAUST WITH ALL BRAKES RELEASED Check anti-compound double check valve #16. Check #20 and #18A & 18B for back flow into service controlline. Check trailer air system for back flow into Tractor s servicecontrol line. Check seal in spring brake for back-flow of spring hold-off pressure through service port to open exhaust on #15 Spring Parking Brake. CAUTION: CHOCK WHEELS - REPAIR AND REPLACE ITEMS ASNECESSARY. LEAKS AT EXHAUST WITH HAND VALVE APPLIED Check double check valve #23 or #24.

7 Repair or replace. LEAKS AT EXHAUST WITH FOOT BRAKE APPLIED Foot valve defective. Repair or replace. LEAKS AT EXHAUST WITH ALL PARK BRAKES SET IN PARKPOSITION AND FOOT BRAKE RELEASED Foot valve defective. Repair or RELEASE VALVE LEAKS AT EXHAUST PORT WITH ALL BRAKES RELEASED Check and replace #18A & 18B if back flow occurs intosecondary control line. LEAKS WHEN SERVICE BRAKES ARE APPLIED Repair or BRAKE CHAMBER FOR Troubleshooting INFORMATION REFER TO THE OEMOPERATING ADJUSTER FOR Troubleshooting INFORMATION REFER TO THE OEMOPERATING INSTRUCTIONS. NOTE: If the slack adjusters are manufactured by MeritorWABCO, refer to Meritor Maintenance Manual 4B (AutomaticSlack Adjusters) or contact the Meritor Customer SupportCenter at 800-535-5560 (001-800-889-1834 desde Mexico).RELAY VALVE LEAKS AT EXHAUST PORT WITH ALL BRAKES RELEASED Check seal in spring brake for back-flow of spring hold-off pressure through service port to open exhaust on #15 Spring Parking Brake.

8 Check reservoir port for evidence of contamination, checksupply lines for rusty fittings or carbon deposits. Repair orreplace. LEAKS AT EXHAUST PORT WITH SERVICE BRAKES APPLIED Exhaust 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 COMBINATION FOOT VALVE EXHAUST LEAK PARK BRAKES RELEASED YELLOWDASH CONTROL V VALVE EXHAUST LEAK IN PARK POSITIONAND SERVICE BRAKES APPLIED Check anti-compound double check valve portion for feedbackto foot or dash control valve. Repair or LIGHT SWITCH LEAKS Replace. FAILS TO SIGNAL A GOOD BULB THROUGH SOUND WIRING AT3-6 Replace. TOWING TRUCK OPTIONSINVERSION RELAY VALVE WITH THE LOSSOF REAR SERVICE BRAKES,APPLICATION OF SPRING BRAKE BYUSING THE EMERGENCY SECTIONSHOULD BE AVAILABLE ALONG WITHFRONT SERVICE BRAKE BY APPLYINGFOOT VALVE PERIODICALLY TEST BY BLEEDING REAR SERVICE TANK ANDOBSERVING FRONT BRAKE AND REAR SPRING BRAKEAPPLICATION UPON DEPRESSING FOOT PEDAL.

9 REPAIR ORREPLACE, IF AFTER CHECKING INVERSION VALVE IS NOTFUNCTIONING PROPERLY. LEAKS Repair or DRYER AIR LEAKING CONSTANTLY FROM PURGE VALVE Purge valve seal damaged. Replace. Purge valve frozen. Inspect heater (see heater problems). HEATER INOPERATIVE Blown Fuse. Check fuse and replace with 8-10 amp fuse. Broken wires or poor connections. Repair or replace wiringto heater. SLOW SUPPLY (WET TANK) BUILD-UP Filter and/or desiccant plugged. Service air dryer. If a SystemSaver Series air dryer is installed, refer to Meritor WABCOM aintenance Manual 34 (Single Canister) or 35 (TWIN) foradditional Troubleshooting information or contact the MeritorCustomer Support Center at 800-535-5560(Ilamasin costo desde Mexico 001-800-889-1834).ABS ELECTRONIC CONTROL UNIT,MODULATOR VALVES, SENSORS, ANDTOOTH RINGS1255436789101112131415161718A18B192 0B2020A2223242521