Bendix Commercial Vehicle Systems AD-4 AIR DRYER 10/04 - Manual (Page 19)

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I. Desiccant requires
replacement.
AD-4 ™ AIR DRYER TROUBLESHOOTING CHART (Continued)
SYMPTOMS CAUSE REMEDY
H. If vehicle uses Holset compressor, inspect
feedback check valve for proper installation and
operation.
When replacing the desiccant cartridge, make
sure desiccant cartridge assembly is properly
installed and sealing rings are in place on
mounting surface of desiccant cartridge.
H. Air by-passes desiccant
cartridge assembly.
I. 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. Air brake charging
system is functioning
normally.
3. Oil present at air dryer
purge exhaust or
cartridge during
maintenance.
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).
A. Restriction between air
dryer and supply (first)
reservoir.
B. Air dryer safety valve
malfunction.
C. Desiccant cartridge
maintenance required.
D. Malfunctioning discharge
check valve in end cover
of the AD-4
™ air dryer.
E. Excessive pressure
pulsations from
compressor. (Typical
single cylinder type).
4. Safety valve on air dryer
“popping off” or
exhausting air.