Air Dryer Troubleshooting Guide

Fleet Products Ltd. · Air Dryer Systems

Air Dryer Troubleshooting Guide

Use this guide to review common air dryer symptoms and likely causes in heavy-duty air brake systems.

PDF Air dryer – troubleshooting guide Open document →

Air Dryer Is Constantly Cycling or Purging

Step Check / Likely Cause
1 Test fittings, 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 or 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.

Air Dryer Does Not Purge or Exhaust

Step Check / Likely Cause
1 Missing, broken, kinked, frozen, plugged or disconnected purge valve control line.
2 Faulty air dryer purge valve.

Air Dryer Purge Piston Cycles Rapidly During Compressor Unloading Cycle

Step Check / Likely Cause
1 Compressor is failing to unload, check unloader.

Constant Exhaust of the Purge Valve

Step Check / Likely Cause
1 Purge valve internal leak.
2 Compressor failing to unload.
3 Purge control line connected to wrong place, reservoir or wrong port on governor.
4 Purge valve frozen open, check heater is working.

Pop Off Valve Is Blowing at the Air Dryer or the Air Compressor

Step Check / Likely Cause
1 Restrictions 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.

Cannot Build System Air Pressure

Step Check / Likely Cause
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.

Oil Present at the Air Dryer

Step Check / Likely Cause
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.

Desiccant Material Being Expelled From Air Dryer or Becomes Paste-Like Appearance

Step Check / Likely Cause
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.

Noise in Air Dryer During Compressor Charging Cycle

Step Check / Likely Cause
1 Defective check valve in air dryer.
2 Leaking turbo cut-off valve.
3 Leaking purge valve control piston O-ring.

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