GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 1999 🢒 Isuzu MD Steel Tilt (F Model) 🢒 Brakes 🢒 Air Brakes 🢒 Trailer Brake Control Valve Operational Check

Trailer Brake Control Valve Operational Check Operational Check

  1. Block the wheels.
  2. Drain all of the air reservoirs. Refer to Draining Reservoirs
  3. Install a test air pressure gauge in the trailer air brake control valve delivery line.
  4. Start the engine.
  5. Charge the system to the air compressor governor cut-out point.
  6. Stop the engine.

    7. Object Number: 227705 Size: SH
  7. Push the trailer air brake control lever down to the full OFF position.
  8. Verify that the test air pressure gauge indicates zero air pressure.

    9. If the gauge does not indicate zero air pressure, replace the trailer air brake control valve.

  9. Pull up on the trailer air brake control lever to the full ON position.
  10. Verify that the test air pressure gauge indicates the same air pressure as the the dual air pressure gauge.

    11. If the test air presssure gauge and the dual air pressure gauge do not have the same air pressure reading then replace the trailer air brake control valve.

  11. Move the lever to several intermediate positions.
  12. Verify that the test air pressure gauge indicates intermediate air pressures consistent with the handle position.
  13. Drain all of the air reservoirs.
  14. Remove the test air pressure gauge.
  15. Start the engine.
  16. Charge the system to the air compressor governor cut-out point.
  17. Stop the engine.
  18. Check for proper brake operation.
  19. Remove the wheel blocks.

Trailer Brake Control Valve Operational Check Leakage Test

  1. Block the wheels.
  2. Start the engine.
  3. Charge the system to the air compressor governor cut-out point.
  4. Stop the engine.

    5. Object Number: 227705 Size: SH
  5. Push down the trailer air brake control valve lever to the full OFF position.
  6. Inspect the valve body and the exhaust port for air leakage. Air leakage is not permissible.

    7. If air leakage is present, replace the trailer air brake control valve.

  7. Pull up the trailer air brake control lever to the full ON position.
  8. Inspect the valve body and the exhaust port for air leakage. Air leakage is not permissible.

    9. If air leakage is present, replace the trailer air brake control valve.

  9. Remove the wheel blocks.