3
Troubleshooting and Testing
28
Meritor WABCO
Maintenance Manual 34 (Revised 03-16)
Air dryer purges too
often, perhaps as
frequently as every
15 seconds,
accompanied by
excessive cycling of
the compressor.
Leak in line between governor
and dryer port 4.
Yes
No
Repair air line.
Leak in line between supply tank
and governor.
Yes
Yes
Repair air line.
Leaks in the air system.
Yes
Yes
Repair leaks.
Excessive air system demands.
Yes
Yes
Increase air system capacity or reduce
air demand.
Outlet check valve not seating.
Yes
Yes
Inspect and replace outlet check valve
as needed.
Regeneration valve not shutting
off properly.
Yes
No
Replace regeneration valve.
Air governor has less than 16
psi (110 kPa) range.
Yes
Yes
Replace air governor.
Leaking air compressor
unloader(s).
Yes
Yes
Inspect compressor. Repair/replace per
manufacturer’s instructions.
Air flows out of
purge valve entire
time compressor is
unloaded.
NOTE:
With U Series
air dryers, the
compressor unloads
through the dryer, so a
steady flow of air is
normal.
Turbo cut-off valve not sealing.
Yes
Yes
Replace turbo cut-off valve.
Outlet check valve not seating.
Yes
Yes
Replace outlet check valve.
Rapid “spitting” of
air from purge valve
in small amounts.
Frequency varies
with engine speed.
NOTE:
With U Series
air dryers, the
compressor unloads
through the dryer, so a
steady flow of air is
normal.
Holset E-type compressor used,
but no Econ valve installed.
Yes
Yes
Install Econ valve to provide make-up air
to compressor.
Compressor not completely
unloading when cut-out
pressure is reached.
Yes
Yes
Inspect compressor. Repair/replace per
manufacturer’s instructions.
Condition
Possible Cause
Conditions May Occur In:
Solution
Regeneration
Style Air
Dryers
Dedicated
Purge Tank
Air Dryers
Summary of Contents for 1200E
Page 4: ...Notes...
