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Trailer Testing

Trailer Testing

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Trailer Testing

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  1. Trailer Testing

  2. FACTS AND FIGURES CVSA ROADCHECK June 2-4, 2009 57,013 vehicles inspected 19.6% vehicles were placed Out Of Service 11.6% sidelined for Light System 24.7% sidelined for Brake Adjustment 26.9% sidelined for Brake System CVSA determined 60% of brake OOS could have been corrected in the pre trip inspection

  3. FACTS AND FIGURES LIGHTING ISSUES 90% of discarded incandescent lamps were operational Majority of electrical circuit problems are caused by: Poor connections Road treatment chemicals

  4. FACTS AND FIGURES BRAKE ISSUES Automatic slacks Must still be maintained & adjusted Brake Inspection Technician must be at the axel to witness movement

  5. FACTS AND FIGURES ABS ISSUES Majority of ABS problems are sensor related Over 50% of ECU’s returned under warranty were functional ABS operation is now being checked during State DOT Inspections

  6. FACTS AND FIGURES • TMC Survey • 18% of technicians time is spent on diagnostics • Pro-active maintenance is less costly than road repairs • The electrical and air braking systems on today's trailers require diagnostic equipment

  7. FACTS AND FIGURES • TMC Goals • Reduce vehicle downtime • Diagnostic Equipment must be easy to operate • Diagnostic equipment should have less than one year payback

  8. Trailer testing and maintenance practices need to protect the trailer systems from premature failure • This means applying regulated known electrical power and air pressures during the testing FACTS AND FIGURES • Excessive and non-regulated 12v power damages wiring, • lighting components, and ABS electronics. • Excessive air pressure stresses the air system components. • Low power and low air applications are not reliable for • consistent testing.

  9. For Your Safety, Chock Wheels and Observe Company Policies For Wearing Safety Equipment.

  10. IF there is an unreliable 12 volt dc power source… COMMON LIGHT TESTING High voltages over 13.8v create half life conditions on lighting and ABS components Unregulated voltage spikes (battery chargers) cause damage Low voltages cause dim lights and none operative electronics

  11. COMMON LIGHT TESTING IF all circuits are powered on together… • Circuit shorts will disguise other problems • Non-functional elements will not be obvious in dual element lamps • Incorrect wired lamps will not be seen

  12. OPERATE ONE CIRCUIT AT A TIME PROPER LIGHT TESTING Observe circuit voltage & amperage Technician must verify each lamp operation and location Circuit faults will be discovered Open Short Open ground Chassis ground Brake light and Auxiliary electrical circuits are critical for ABS operation Auxiliary is primary power and is the Power Line Carrier (PLC) The Brake circuit is secondary power and activates ECU operation


  14. Emergency air system releases the parking brakes and is the supply for service operation. COMMON TRAILER BRAKE TESTING Service (brake) system is the control system by drawing air from the supply system thru the relay valve. IF unregulated air pressure is being applied… Excessive Pressures cause damage Insufficient Pressure causes inaccurate results Brake Compounding… Damage slacks Create air leaks Potential for technician injury

  15. PROPER TRAILER BRAKE TESTING IDEAL testing duplicates the tractor operation • Use regulated air pressure matching tractor operation • Emergency/supply application of 110-120 psi • Service/control application at 85-90 psi • Equals a panic stop • Consistent service pressure is required for reliable and accurate brake adjustment

  16. For Your Safety, Chock Wheels Before Applying Air.

  17. VISUAL INSPECTION OF BRAKE MOVEMENT AT AXLE IS REQUIRED • Apply emergency (supply) air • Service brake (control) application requires full supply pressure • Cycle air application • Make slack adjustments • Air leak test with applied emergency and service air • Air loss on one side is external • Equalizing air pressure is internal seal failure • FEDERAL allowable air loss… • 3 psi/minute on emergency(supply) air system • 2 psi/minute on service air system PROPER TRAILER BRAKE TEST PROCESS


  19. Beginning in 1998 all new commercial trailers and dollies were equipped with the blink code style ABS. The Power Line Carrier (PLC) style ABS was mandated in 2001. All have ABS warning lights indicating operation status. As of 2009, approximately 30% of all trailers and dollies have ABS. ABS testing requires filtered regulated 12 volt dc power from a battery or power supply. ABS FACTS

  20. ABS FACTS • TMC has (2) Recommended Practices for ABS operation: • RP 137 specifies the tractor Auxiliary output voltage to be a minimum of 10 volts measured at the vehicle cable trailer plug. • RP 141 specifies 8.5v is required at the ABS Electronic Control Unit with the entire trailer systems powered. NOTE: The ABS Electronic Control Unit (ECU) will not power up with low voltage.

  21. ANTILOCK BRAKE SYSTEM (ABS) operation depends upon the Auxiliary electrical and Brake light circuits. • Auxiliary circuit is the primary power of the Electronic Control • Unit (ECU). • When the ignition switch is turned on, the auxiliary • circuit is energized. • The ECU commences a self test (valve clicks) • The ABS warning light turns on. • Stays on with active fault present • Turns off without a active fault • Brake circuit controls ABS operation • Activates ABS operation whenever brakes are applied • Backup power whenever Auxiliary power is not present • (momentary delay occurs before the ECU is activated). ABS OPERATION

  22. The PLC style ABS can be fully tested at the 7w nose socket. • FIRST: • Energize Brake circuit to verify good operation. The valves will • click and the ABS warning lamp will illuminate. • Initial amperage will include brake lights, ECU load, and ABS warning lamp. • If ABS lamp turns off, the brake lights and ECU amperage load will be displayed. RECOMMENDED ABS TEST PROCESS

  23. SECOND: • Energize Auxiliary circuit for ABS. • If ABS valves do not click, then… • ECU is faulty or Auxiliary circuit has a fault • If ABS valves do click without warning lamp, then… • ABS lamp has a fault • If the ABS warning lamp stays on with Auxiliary power, then… • there is an active ABS fault. • Initial amperage will include ECU load and ABS warning • lamp • If ABS lamp turns off, the ECU amperage will be displayed RECOMMENDED ABS TEST PROCESS

  24. ABS TEST

  25. ONE TOOL • ONE PERSON • ONE PROCESS COMPREHENSIVE TRAILER TESTING • Single tool with diagnostic features • One person operation that is simple to use • Consistent process • Perform trailer DOT test within 10 minutes including brake • adjustments • Reduce repair costs because of accurate diagnostics • Improve on time delivery with road worthy equipment • Reduce road costs including downtime, OOS violations, road • service


  27. GOOD MAINTENANCE=GOOD BUSINESS CUSTOMER COMMENT: “We are using the INSPECTOR in the shop on each trailer that comes in for service. When we make a repair, we are also using it post-repair to certify expected results. We know the repairs are effective and the unit is ready for duty. I just believe our less-experienced techs benefit from the tool and I sleep better at night.”

  28. REFERENCES Federal Motor Carrier Safety Administration Rules & Regulations Commercial Vehicle Safety Alliance (CVSA) ABS - Operation Air Brake - National Highway Traffic Safety Administration (NHTSA) Technology & Maintenance Council (TMC) Canadian Transportation Equipment Association (CTEA) -