For 1990-2009 cars

Problem | Action
--- | ---
The air brake desiccant cartridge is plugged or saturated with contaminants. | Replace the desiccant cartridge.
The internal check valve is faulty. |

1. Remove the check valve from the assembly from the end cover.
2. Apply air pressure to the delivery side of the valve.
3. Apply a soap solution at the opposite end.
4. Inspect for leakage. A permissible leakage is a 25 mm (1 in) bubble in 5 seconds.
5. If the leakage is excessive, replace the check valve.

The fittings or the tubing between the air brake dryer and the supply reservoir are faulty. | Determine if air is reaching the supply reservoir. Inspect the reservoir for kinked tubing or for restricted tube fittings.