Use this guide to review common air dryer symptoms and likely causes in heavy-duty air brake systems.
| AIR DRYER IS CONSTANTLY CYCLING OR PURGING |
| 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 |
| 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 |
| 1 |
Compressor is failing to unload, check unloader. |
| CONSTANT EXHAUST OF THE PURGE VALVE |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 1 |
Defective check valve in air dryer. |
| 2 |
Leaking turbo cut-off valve. |
| 3 |
Leaking purge valve control piston O-ring. |
