CDL Air Brakes TestInspecting Air Brake SystemsHard
A driver is performing a pre-trip inspection. They notice that the air pressure gauge shows a steady 125 psi, but the air compressor cycles on and off much more frequently than usual, even without heavy braking. What is the most likely issue?
- AThe air compressor governor is stuck in the 'cut-in' position.
- BA leak in the air system.
- CThe air dryer is malfunctioning and not purging.
- DA faulty low air warning device.
Show answer & explanationAnswer & explanation
Correct answer: B. A leak in the air system.
If the air compressor cycles frequently even at full pressure and without braking, it indicates that the air system is losing pressure rapidly. This is a classic symptom of a significant air leak somewhere in the system.
Why the other options are wrong
- A. A governor stuck in the 'cut-in' position would mean the compressor runs continuously, not cycles frequently.
- C. A malfunctioning air dryer not purging would not directly cause frequent compressor cycling unless it's also causing a significant leak.
- D. A faulty low air warning device would not cause the compressor to cycle more frequently.
Frequent Compressor Cycling
Frequent cycling of the air compressor, especially at full system pressure without heavy braking, is a strong indicator of an air leak within the brake system.
- Compressor works harder to maintain pressure.
- Leads to increased wear on compressor and engine.
- Requires thorough leak detection and repair.
Memory trick: Compressor's working hard, a hidden leak's its card!