Home › CDL Practice Tests › Air Brakes Questions › Question 57
How do you test the low air pressure warning during a pre-trip inspection?
- A.With the engine off, fan the brakes to bleed air and confirm the warning activates before pressure drops below 60 psi
- B.Rev the engine until the warning sounds
- C.Disconnect the battery and listen for a click
- D.Press the warning lamp lens with a finger
Correct answer
A. With the engine off, fan the brakes to bleed air and confirm the warning activates before pressure drops below 60 psi
Why
Pumping the pedal with the engine off steadily lowers tank pressure under controlled conditions. The driver watches the gauge and confirms the light and buzzer appear above the 60 psi floor.
Manual topic: Air Brakes - Safety Valve and Low Pressure Warning · From the Air Brakes practice bank (AB-057).