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Air Dryer Troubleshooting Guide

The purpose of an air dryer is to collect and remove air system contaminants in solid, liquid, and vapor form before they can enter the air brake system. This allows clean dry air to enter into the air system protecting all its various components. There are two basic operation modes of most common air dryers today, the ‘charge cycle’ and the ‘purge cycle’. Occasionally during these cycles problems can arise for various reasons. We hope this guide will help you to diagnose your air dryer problem.

Dryer Plumbing

Cap

PROBABLE CAUSE TABLE

	Air dryer is constantly cycling or purging
1	Test fitting, hoses, lines and connections with soapy water. Tighten or replace as necessary.
2	Test accessories that are connected to the supply reservoir.
3	Test governor for leakage, either internal of external leak.
4	Test outlet check valve on air dryer.
5	Be sure dryer application is correct if you have QE or E-type, ®Cummins engine.

	Pop off valve is blowing at the air dryer or the air compressor
1	Restriction between air dryer and supply reservoir.
2	Dryer cartridge needs to be serviced.
3	Discharge line from the compressor to the air dryer plugged or frozen.
4	Malfunction of the safety valve.

	Oil present at the air dryer
1	Time for regular maintenance.
2	Air compressor needs repair.
3	Remember some oil is normal, if oil is getting past dryer to first air tank, compressor repair must be done and air dryer serviced.

	Cannot build system air pressure
1	Inlet and outlet connections are reversed.
2	The check valve between the dryer and first tank may be restricted.
3	Kinked or blocked discharge line.
4	Excessive bends in discharge line, oil turns to carbon in line, water freezes in line between compressor and first tank.

	Air dryer does not purge or exhaust
1	Missing, broken, kinked, frozen, plugged or disconnected purge valve control line.
2	Faulty air dryer purge valve.

	Noise in air dryer during compressor charging cycle
1	Defective check valve in air dryer.
2	Leaking turbo cut-off valve.
3	Leaking purge valve control piston o-ring.

	Air dryer purge piston cycles rapidly during compressor unloading cycle
1	Compressor is failing to unload, check unloader system.

	Desiccant material being expelled from air dryer or becomes paste like in appearance
1	Air dryer not securely mounted to frame causing vibration.
2	Malfunction or saturated desiccant.
3	Compressor passing excessive oil.
4	Chemicals such as alcohol added to discharge line before the air dryer.