13
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 a soap solution, test the vehicle for leakage at the
fittings, drain valves, 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 the system pressure to governor cut-out. Wait 1 minute for
completion of purge cycle. Using a soap solution at the exhaust
of the purge valve, leakage should not exceed a 1 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 the 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 inch 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 the air strainer, or fitting, from the compressor inlet
cavity. With the compressor unloaded, check for unloader piston
leakage. Slight leakage is permissible.
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