11
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 dash gauge:
- Single vehicle - 1 psi/minute.
- Tractor trailer - 3 psi/minute.
Using soap solution, test vehicle for leakage at fi ttings,
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
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 “fan” 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 1" bubble in 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 governor at both “cut-in” and “cut-out” position for (i)
proper pressures and (ii) excessive leakage at fi ttings and
exhaust.
D. Compressor unloader mechanism
leaking excessively.
D. Remove air strainer, or fi tting, from compressor inlet cavity.
With compressor unloaded, check for unloader piston
leakage. Slight leakage is permissible.
