CDL General Knowledge TestAir Brakes (if applicable)Easy
A commercial vehicle with air brakes has just been started. The driver notices that the air pressure gauges are slowly rising, but the low air pressure warning light and buzzer remain active. At what minimum air pressure PSI should these warnings deactivate?
- A30 PSI
- B80 PSI
- C100 PSI
- D60 PSI
Show answer & explanationAnswer & explanation
Correct answer: D. 60 PSI
The low air pressure warning system is designed to alert the driver when the air pressure in the primary or secondary air tank falls below a safe operating level. These warnings must deactivate when the pressure rises above 60 PSI.
Why the other options are wrong
- A. This pressure is too low; warnings would still be active.
- B. This pressure is well above the minimum deactivation point.
- C. This pressure is close to the full operating pressure, far above the deactivation point.
Low Air Warning Deactivation
The low air pressure warning light and buzzer in an air brake system must deactivate when the air pressure rises to a safe operating level.
- Activates below 60 PSI
- Deactivates at or above 60 PSI
- Indicates insufficient pressure for safe braking
Memory trick: Sixty PSI is the safety key, warnings off, you're good to see.