Bendix Commercial Vehicle Systems AD-9si Oil Coalescing Air Dryer - Manual (Page 13)

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BENDIX ® AD-9si ™ AIR DRYER
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 dash gauge:
- Single vehicle - 1 psi/minute.
- Tractor trailer - 3 psi/minute.
Using soap solution, test vehicle for leakage at fittings,
drain valves and system valves and any accessories (i.e.
air suspension). Repair or replace as necessary and retest
the system.
B. Defective delivery check valve. B. Build system pressure to governor cut-out. Wait 1 minute for
completion of purge cycle. Using soap solution at exhaust of
purge valve, leakage should not exceed a 1" 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 multiple times so that the system pressure reaches
governor cut-in. The purge valve will return to its closed
position. 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 1" bubble in 5 seconds).
Re-grease the seal on the air dryer cartridge before
reinstalling.
C. Defective governor. C. Check governor at both “cut-in” and “cut-out” position for
proper pressures and excessive leakage at the exhaust.
D. Compressor unloader mechanism
leaking excessively.
D. Remove air strainer, or fitting, from compressor inlet cavity.
With compressor unloaded, check for unloader piston
leakage. Slight leakage is permissible.