Bendix Commercial Vehicle Systems AD-4 AIR DRYER 10/04 - Manual (Page 20)

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AD-4 ™ AIR DRYER TROUBLESHOOTING CHART (Continued)
D. Excessive bends in
discharge line (water
collects and freezes).
E. Refer to Symptom 4,
causes E & F.
SYMPTOMS CAUSE REMEDY
F. Governor malfunction.
Missing or restricted
governor control line
installation.
F. Test governor operation and/or inspect the
control line leading from the governor UNL
(unloader) port to the air dryer control port.
5. Constant exhaust of air
at air dryer purge valve
exhaust. (Charge
mode.)
A. Air dryer purge valve
leaking excessively.
B. Compressor fails to
unload (stop
compressing air) and air
dryer purge exhaust
makes “sputtering” or
“popping” sound.
C. Purge control line
connected to reservoir or
exhaust port of governor.
D. Purge valve frozen open -
malfunctioning heater
and thermostat, wiring,
blown fuse.
A. With compressor loaded, apply soap solution
on purge valve exhaust, to test for excessive
leakage. Repair purge valve as necessary.
B. Confirm failure to unload by increasing &
decreasing engine RPM and noting change in
the rate of leakage and intensity of
accompanying leakage sound. Repair/replace
compressor unloaders.
C. Purge control line must be connected to
unloader port of governor.
D. Test heater and thermostat as described in
Preventative Maintenance Section.
E. See Symptom #1. E. Excessive system
leakage.
F. Purge valve stays open -
supply air leaks to
control side.
F. Repair purge valve and housing.
6. Can not build system air
pressure.
A. Inlet and outlet air
connections reversed.
B. Check valve between air
dryer and first reservoir.
C. Kinked or blocked
(plugged) discharge line.
A. Connect compressor discharge to air dryer
supply port. Reconnect lines properly.
B. Test check valve for proper operation. Repair or
replace as necessary.
C. Check to determine if air passes through
discharge line. Check for kinks, bends,
excessive carbon deposits, or ice blockage.
D. Discharge line should be constantly sloping from
compressor to air dryer with as few bends as
possible.
E. Refer to Symptom #4, Remedies E & F.
7. Air dryer does not purge
or exhaust air.
A. Missing, broken, kinked,
frozen, plugged or
disconnected purge
control line.
A. Inspect control line from governor UNL (unloader)
port to control port of air dryer. Test to determine
air flows through purge control line when
compressor unloaded. Check for undrilled
fittings. (See Symptom #4, Remedy C.)
B. After determining air reaches purge valve
(Remedy A above), repair purge valve.
C. Refer to Remedies B, E, G for Symptom #4.
B. Faulty air dryer purge
valve.
C. See Causes, B, E, G for
Symptom #4.