BENDIX BW1948 manual DRM/AD-ISAIR Dryer Troubleshooting Chart

DRM™/AD-IS®AIR DRYER TROUBLESHOOTING CHART

SYMPTOMS	CAUSE	REMEDY
1. Dryer is constantly	A. Excessive system	A. Test for excessive system leakage.
“cycling” or purging.	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. Repair
		or replace as necessary.
	B. Defective delivery check	B. Build system pressure to governor cut-out. Wait
	valve.	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 boss.
		Replace the delivery check valve if there is
		excessive leakage (exceeding a 1" bubble in 5
		seconds).
		Regrease 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 fittings and exhaust.
	D. Compressor unloader	D. Remove air strainer or fitting from compressor
	mechanism leaking	inlet cavity. With compressor unloaded, check
	excessively.	for unloader piston leakage. Slight leakage
		permissible.

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