Bendix Commercial Vehicle Systems AD-IS AIR DRYER AND RESERVOIR SYSTM - Manual (Page 13)

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BENDIX ® AD-IS ® AIR DRYER AND RESERVOIR SYSTEM
TROUBLESHOOTING CHART
SYMPTOM CAUSE REMEDY
1. Dryer is constantly “cycling”
or purging.
A. Excessive system leakage. A. Test for excessive system leakage. Allowable leakage
observed at the dash gauge:
- Single vehicle - 1 psi/minute.
- Tractor trailer - 3 psi/minute.
Using a Bensoap solution, test vehicle for leakage at the
fittings, drain valves and system valves and any accessories
(i.e. air suspension) connected to the Bendix ® AD-IS ® air dryer
auxiliary ports. If an accessory is suspected to be the cause
of leakage, disconnect that accessory from the air dryer, plug
the auxiliary port that it was in, and retest the AD-IS air dryer
for proper purge cycling. Repair or replace as necessary.
B. Defective delivery check valve. B. Build system pressure to governor cut-out. Wait 1 minute for
the completion of the purge cycle. Using a soap solution at
the exhaust of the purge valve, leakage should not exceed
a one inch bubble in less than 5 seconds.
If a rapid loss of pressure is found, the following procedure
will determine if the delivery check valve is malfunctioning:
Build system pressure to governor cut-out and allow a full
minute for the normal dryer purge cycle to empty the purge
reservoir. Switch off the engine and apply and release the
brakes so that the system pressure reaches governor cut-in.
The purge valve will return to its closed position. The purge
reservoir has a drain valve which is opened by moving the
center lever away from its closed position. Open the drain
valve and wait 10 seconds to allow any residual purge
pressure to be released. Release the lever, closing the drain
valve. Carefully remove the air dryer cartridge using a strap
wrench and then test for air leaking through the center of
the threaded boss by applying a soap solution to the area.
Replace the delivery check valve if there is excessive leakage
(exceeding a one inch bubble in five 5 seconds).
Re-grease the seal on the air dryer cartridge before
reinstalling. Be sure the drain valve on the purge reservoir
is not leaking before restoring vehicle to service.
C. Defective governor. C. Check the governor at both the “cut-in” and “cut-out” position
for (i) proper pressures and (ii) excessive leakage at fittings
and exhaust.
D. Compressor unloader mechanism
leaking excessively.
D. Remove the air strainer, or fitting, from compressor inlet
cavity. With the compressor unloaded, check for unloader
piston leakage. Slight leakage is permissible.