CDL Air Brakes TestUsing Air BrakesMedium
A commercial driver is performing a pre-trip inspection and notices that the air compressor's automatic shut-off occurs at 125 psi, but it doesn't restart until the pressure drops to 85 psi. What component is likely malfunctioning?
- AThe air dryer
- BThe governor
- CThe safety relief valve
- DThe foot valve (brake pedal)
Show answer & explanationAnswer & explanation
Correct answer: B. The governor
The governor controls when the air compressor starts and stops. Its settings determine the cut-in and cut-out pressures. A wide or incorrect pressure range indicates a potential governor malfunction.
Why the other options are wrong
- A. The air dryer removes moisture from the air, but doesn't control compressor on/off cycles.
- C. The safety relief valve protects against over-pressurization but doesn't control the normal operating range.
- D. The foot valve applies the brakes and releases air from the system, but doesn't regulate compressor operation.
Air Compressor Governor
A component in the air brake system that regulates the air compressor, ensuring it maintains air pressure within a specified operating range by controlling its start and stop points.
- Controls compressor cut-in and cut-out pressures.
- Typically cuts out around 125 psi.
- Typically cuts in around 100 psi.
Memory trick: Governor: 'Controls Compressor's Cycles'