CDL Air Brakes TestInspecting Air Brake SystemsHard
A technician is troubleshooting an air brake system where the air dryer continuously purges even when the system pressure is stable and full. What is the most likely cause?
- AA clogged air dryer desiccant cartridge.
- BA leak in the air dryer's purge valve or control line.
- CA faulty air compressor governor.
- DA stuck open one-way check valve in the wet tank line.
Show answer & explanationAnswer & explanation
Correct answer: B. A leak in the air dryer's purge valve or control line.
If the air dryer continuously purges, it suggests that the purge valve is not sealing correctly or its control line has a leak, causing it to remain open or cycle erratically, leading to constant air loss.
Why the other options are wrong
- A. A clogged desiccant cartridge would reduce drying efficiency, but not cause continuous purging.
- C. A faulty governor would affect compressor cut-in/cut-out, not directly cause continuous dryer purging.
- D. A stuck open check valve in the wet tank line would prevent pressure build-up or cause backflow, not continuous purging.
Air Dryer Continuous Purging
Continuous purging of an air dryer, even at stable system pressure, indicates an issue with the purge valve or its control mechanism, causing constant air loss.
- Purge valve stuck open or leaking.
- Control line leak to the purge valve.
- Leads to excessive air consumption and compressor cycling.
Memory trick: Constant hiss? Purge valve amiss!