CDL Air Brakes TestUsing Air BrakesEasy
A commercial driver is conducting a pre-trip inspection of their air brake system. They observe that the air pressure in the primary and secondary tanks is at 125 psi. What is the typical range for the governor to cut-out the air compressor?
- A80-90 psi
- B100-110 psi
- C120-140 psi
- D60-70 psi
Show answer & explanationAnswer & explanation
Correct answer: C. 120-140 psi
The air compressor governor is designed to cut-out, or stop compressing air, when the air tanks reach their maximum operating pressure. For most commercial vehicles, this range is typically between 120 and 140 psi to ensure sufficient air supply for braking.
Why the other options are wrong
- A. This range is well below the normal operating pressure for a fully charged air brake system.
- B. This range is typically where the governor cuts-in, starting the compressor, not cutting it out.
- D. This range is dangerously low and would trigger a low air pressure warning, indicating a severe problem.
Governor Cut-Out Pressure
The air pressure at which the air compressor governor stops the compressor from pumping air into the storage tanks.
- Typically occurs between 120-140 psi.
- Prevents over-pressurization of the air brake system.
- Ensures adequate air supply without wasting energy.
Memory trick: The governor smartly cuts off when pressure is high.