15
BENDIX
®
AD-9si
®
AIR DRYER
TROUBLESHOOTING CHART
SYMPTOM CAUSE REMEDY
5. Cannot build system air
pressure.
A. Supply pressure to the air dryer is not
sufficient.
A. Ensure the supply pressure to the air dryer is greater than
110 psi during the system charge.
B. Kinked or blocked (plugged) discharge
line.
B. Check to determine if air passes through the discharge line.
Check for kinks, bends, excessive carbon deposits, or ice
blockage.
C. Excessive bends in discharge line (water
collects and freezes).
C. The discharge line should be constantly sloping from the
compressor to the air dryer with as few bends as possible.
D. Refer to Symptom 4. D. Refer to Symptom 4, Remedy A.
E. Refer to Symptom 7. E. Refer to Symptom 7, Remedies A and B.
6. Air dryer does not purge or
exhaust air.
A. Faulty air dryer purge valve. A. After determining that air reaches the purge valve piston – by
installing a Tee fitting with a pressure gauge into the control
port – repair the purge valve if necessary.
B. See Causes B, E, and F for
Symptom #4.
B. Refer to Symptom 4, Remedies B, E, and F.
7. Desiccant material being
expelled from air dryer purge
valve exhaust (may look like
whitish liquid, paste, or small
beads.)
A. Faulty dryer cartridge. A. Replace the Bendix
®
AD-9si
®
air dryer cartridge or AD-9si air
dryer.
B. Excessive dryer vibration. B. Check the AD-9si air dryer mounting for looseness or damage.
Repair the mounting and replace the cartridge.
8. Unsatisfactory desiccant life. A. Excessive system leakage. A. Refer to Symptom 1, Remedy A.
B. Wrong vehicle application for AD-9si
air dryer.
B. Refer to Symptom 2, Remedy C.
C. Compressor passing excessive oil. C. Check for proper compressor installation; if symptoms
persist, replace the compressor. Refer to
Bendix
®
Advanced
Troubleshooting Guide for Air Brake Compressor
(BW1971).
9. “Pinging” noise excessive
during compressor loaded
cycle.
A. Single cylinder compressor with high
pulse cycles.
A. A slight “pinging” sound may be heard during system build-
up when a single cylinder compressor is used. If this sound
is deemed objectionable, it can be reduced substantially by
increasing the discharge line volume.
This can be accomplished by adding a 90 cubic inch (or larger)
reservoir between the compressor and the AD-9si
air dryer.
10. The air dryer purge piston
cycles rapidly in the
compressor unloaded (non-
compressing) mode.
A. Compressor fails to “unload”. A. Check the air hose from the AD-9si air dryer control port to the
compressor for a missing, kinked, or restricted line. Install or
repair the air hose. Repair or replace the compressor unloader.
Check the compressor for a missing, kinked, or restricted line.
Install or repair the air hose.
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