Tests Common to More than ONE Complaint

1. Discharge plugged or restricted

•Connect a temporary discharge line from the compressor discharge port to the supply reservoir and re-check the build-up. If the system build-up is OK then replace the plugged discharge line. If the build-up is NOT OK, go to next cause.

2.Air pressure trapped between the governor and the compressor

•Verify the safety valve operation, then remove or disconnect the governor from the compressor and check build-up.

•If the build-up is OK, repair or replace the governor or the line between the governor and the compressor.

•If the build-up is NOT OK, repair or replace the compressor.

3. Blow Leakage at the Air Dryer Exhaust

•Drain all air from the supply reservoir then remove the control air line from the air dryer, plug the line and plug the control port in the air dryer. Re-check build-up.

•If the build-up is OK, repair or replace the governor or the line between the governor and the air dryer.

•If the build-up is NOT OK, and the temperature is below 32° F, turn the ignition ON and allow the heater to warm the air dryer then check the system build-up. If NOT OK, remove the wire (connector or terminal) from the air dryer. Using a test light, check the wire end, or terminal, for battery voltage with the vehicle ignition ON. If the voltage is OK, repair or replace the air dryer heater and thermostat. If the voltage is NOT OK, repair or replace the vehicle wire connected to the air dryer. Retest build-up.

•If build-up is still NOT OK, or if the temperature is above 32° F, replace the air dryer purge valve assembly.

4. Air system leakage

•Build the system pressure to governor cut-out, wait two (2) minutes for the air dryer purge completion. Note the pressure on the dash gauges then watch the dash gauges for two (2) minutes. The leakage is not to exceed 2 psi in two (2) minutes for truck bus or tractor (no trailer).

•If the leakage is NOT OK on the gauges, find the leak(s) in service and park system and repair. Retest and if the system purge air dryer is in use and still not OK, repair or replace the dryer.

•If the leakage is OK on the gauges, drain the air from the supply reservoir, remove the drain cock and install an air gauge. Build the system air in the supply reservoir and note the leakage. If OK, continue checking. If NOT OK, find the leaks and repair.

5. Discharge line leakage

•Apply a soap solution to the cover on the flexible discharge line, if leakage is noted, replace the line.

•Soap fittings to check for leakage and tighten as needed.

IMPORTANT: The Complaints, Causes and Remedies presented here should not be considered as the only situations possible. They are only meant to represent the most commonly encountered situations. It may be necessary to perform additional troubleshooting using the more detailed information presented in service manuals for the specific components.

Log-on and Learn from the Best

On-line training that's available when you are 24/7/365.

Visit www.brake-school.com.