The air brake dryer desiccant cartridge requires replacement.

Replace the desiccant cartridge.

The air system was charged from an external air source. Air is not passing through the air brake dryer.

Decrease use of the inflation valve in order to charge the system.

The air brake dryer is not purging.

Refer to Air Brake Dryer Does Not Purge or Exhaust Air .

The air brake dryer is not functioning.

Repair or replace as necessary.

The purge (air exhaust) time is too short because of excessive system leakage.

Refer to Desiccant Being Expelled From Purge Valve Exhaust .

The piston rings are worn out.

Overhaul or replace the air compressor.

The air filter is dirty.

Replace the air filter.

The inlet vacuum is high.

Clean or repair as needed.

The air compressor oil outlet hose is restricted.

Remove the restriction or replace the air compressor oil outlet hose.

The engine oil pressure is too high.

1. Determine the cause of the condition.
2. Repair or replace as needed.

The air compressor oil inlet hose is flooded with water.

1. Determine the cause of the condition.
2. Repair or replace as needed.

The air compressor oil outlet hose is flooded with water (gasoline engine).

1. Determine the cause of the condition.
2. Repair or replace as needed.

The air compressor oil outlet return passage is flooded with water (diesel engine).

1. Determine the cause of the condition.
2. Repair or replace as needed.

The piston rings are not properly seated.

Overhaul or replace the air compressor.

The back pressure exists from the engine crankcase.

Determine the cause of the back pressure and repair.