3 Troubleshooting and Testing
27
Meritor WABCO Maintenance Manual 34 (Revised 03-16)
Regeneration cycle
too short (less than
10 seconds).
High air system demands during
compressor unloaded cycle.
Yes Yes Increase air system capacity or reduce
air demands.
Pressure-controlled check valve
not installed in system or not
working properly.
Yes Yes Check and replace pressure-controlled
check valve as needed.
One-way check valve installed in
system reservoir instead of, or
with, pressure-controlled check
valve.
Yes No Remove one-way check valve. Make
sure pressure-controlled check valve is
installed correctly.
Regeneration valve not working. Yes No Remove regeneration valve and clean oil
from diaphragm. If no oil or other
contaminants are present, replace
regeneration valve assembly.
Air governor not working
properly.
Yes Yes Inspect air governor. Repair/replace per
manufacturer’s instructions.
Water in purge tank. Block in purge tank line. N/A Yes Clear blockage. Replace desiccant
cartridge.
No regeneration
cycle. No airflow
from purge valve
after initial purge
blast (dryer
decompression).
Air dryer not connected to
supply tank or connections
reversed at dryer.
Yes No Verify proper dryer installation per
system diagram.
Regeneration valve not working. Yes No Replace regeneration valve.
One-way check valve installed in
supply tank.
Yes No Remove one-way check valve.
Alcohol evaporator installed
between dryer and supply tank.
Yes No Install bypass line around evaporator or
remove evaporator from system.
Blocked line/pinched line from
purge tank.
No Yes Clear/repair line.
Air dryer does not
purge when
compressor unloads
(no blast of air from
purge valve).
Air line between governor and
air dryer port 4 kinked or
plugged.
Yes Yes Repair air line.
Purge valve stuck closed. Yes Yes Replace purge valve.
Air governor not working
properly.
Yes Yes Inspect air governor. Repair/replace per
manufacturer’s instructions.
Cut-out pressure never achieved
by air compressor.
Yes Yes Check for air leaks in system and repair
as needed. If no leaks in system, check
compressor output. Repair/replace per
manufacturer’s instructions.
Condition Possible Cause
Conditions May Occur In:
Solution
Regeneration
Style Air
Dryers
Dedicated
Purge Tank
Air Dryers
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