Service manual

20
E. Excessive pressure
pulsations from
compressor. (Typical
single cylinder type).
F. Governor malfunction.
Missing or restricted
governor control line
installation.
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.
AD-9
™
AIR DRYER TROUBLESHOOTING CHART
SYMPTOMS CAUSE
REMEDY
3. Oil present at air dryer
purge exhaust or
cartridge during
maintenance.
J. Replace desiccant cartridge assembly. Refer to
Appendix A, Table A columns 3 & 4 for
recommended intervals.
A. Air dryers remove water and oil from the air
brake charging system. A small amount of oil is
normal. Check that regular maintenance is being
performed and that the amount of oil in the air
tanks (reservoirs) is within the acceptable range
shown on the BASIC cup (see also column 5 of
Appendix A, Table A.) Replace the air dryer
cartridge as needed and return the vehicle to
service.
A. Check to determine if air is reaching supply
reservoir. Inspect for kinked tubing or hose.
Check for undrilled or restricted hose or tubing
fittings and repair or replace as needed.
B. Verify relief pressure is at vehicle or component
manufacturer specifications. Replace if
malfunctioning.
C. Refer to Appendix A Table A and column 3.
Check compressor for excessive oil passing
and/or correct compressor installation. Repair or
replace as necessary. Replace desiccant
cartridge.
D. Test to determine if air is passing through check
valve. Repair or replace.
E. Increase volume in discharge line by increasing
length or diameter. Add a ping tank (small
reservoir).
F. Test governor operation and/or inspect the
control line leading from the governor UNL
(unloader) port to the air dryer control port.
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.
J. Desiccant requires
replacement.
A. Air brake charging
system is functioning
normally.
A. Restriction between air
dryer and supply (first)
reservoir.
4. Safety valve on air dryer
“popping off” or
exhausting air.
B. Air dryer safety valve
malfunction.
C. Desiccant cartridge
maintenance required.
D. Malfunctioning defective
discharge check valve in
end cover of the AD-9
™
air dryer.
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