Bendix Commercial Vehicle Systems AD-SP SYSTEM PURGE AIR DRYER 10/04 - Manual (Page 30)

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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.
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.
TESTS COMMON TO MORE THAN ONE COMPLAINT
SD-08-2414 © 2014 Bendix Commercial Vehicle Systems LLC, a member of Knorr-Bremse Group • 9/2014 • All rights reserved.
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