CDL Air Brakes TestAir Brake System PartsMedium
A driver performs a brake test and notes that the low air pressure warning light and buzzer activate when the air pressure drops to 55 psi. What action should the driver take?
- AImmediately pull over and have the vehicle inspected, as this indicates a severe malfunction.
- BNote the observation and have the warning system inspected at the next scheduled maintenance.
- CPump the brake pedal rapidly to increase air pressure and reset the warning.
- DContinue driving, as the system is functioning within acceptable limits.
Show answer & explanationAnswer & explanation
Correct answer: A. Immediately pull over and have the vehicle inspected, as this indicates a severe malfunction.
The low air pressure warning system should activate at or above 60 psi. If it activates at 55 psi, it indicates a significant air leak or a faulty warning system, both of which are critical safety concerns requiring immediate attention.
Why the other options are wrong
- B. This is a critical safety issue, not something to wait for scheduled maintenance.
- C. Pumping the brake pedal will *decrease* air pressure, worsening the situation, and will not reset a warning caused by low pressure.
- D. The warning system should activate at no less than 60 psi. 55 psi is below the safe operating threshold.
Low Air Pressure Warning
The low air pressure warning system alerts the driver when air pressure in the primary or secondary tank falls below 60 psi (or half the governor cut-out pressure, whichever is lower).
- Must activate at 60 psi or higher.
- Usually a red light and an audible buzzer.
- Indicates insufficient air for safe braking.
Memory trick: Sixty psi, safety's key!