Troubleshooting Chart

BENDIX®AD-9si™AIR DRYER

SYMPTOM		CAUSE		REMEDY
1. Dryer is constantly “cycling”	A.	Excessive system leakage.	A.	Test for excessive system leakage. Allowable leakage
or purging.				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	D.	Remove air strainer, or fitting, from compressor inlet cavity.
		leaking excessively.		With compressor unloaded, check for unloader piston
				leakage. Slight leakage is permissible.

TROUBLESHOOTING CHART

SYMPTOM

CAUSE

REMEDY