CDL Air Brakes TestUsing Air BrakesMedium
A commercial driver is performing a pre-trip inspection of their air brake system. They notice that the air compressor cuts out at 125 psi and cuts back in at 100 psi. What does this indicate about the air compressor governor?
- AThe governor is operating within normal parameters.
- BThe cut-in pressure is too high and needs adjustment.
- CThe governor is faulty and needs immediate repair.
- DThe cut-out pressure is too low and needs adjustment.
Show answer & explanationAnswer & explanation
Correct answer: A. The governor is operating within normal parameters.
The air compressor governor typically cuts out (stops compressing air) between 100-125 psi and cuts in (starts compressing air again) when pressure drops to 85-100 psi. The observed 125 psi cut-out and 100 psi cut-in are both within the acceptable range for normal operation.
Why the other options are wrong
- B. A 100 psi cut-in is at the higher end but still within the acceptable range (85-100 psi), so it does not necessarily need adjustment.
- C. These readings are normal, so the governor is not faulty based on this information.
- D. A 125 psi cut-out is at the higher end but still within the acceptable range (100-125 psi), so it does not necessarily need adjustment.
Air Compressor Governor Operation
A component in an air brake system that controls when the air compressor starts and stops, maintaining system air pressure within a safe and efficient range.
- Cuts out (stops) between 100-125 psi.
- Cuts in (starts) between 85-100 psi.
- Maintains optimal air pressure.
- Essential for air brake function.
Memory trick: Governor: High (Cut Out) and Low (Cut In) keeps the air flow.