CDL Air Brakes TestInspecting Air Brake SystemsEasy
A driver is performing a pre-trip inspection on a vehicle with air brakes. They notice that the air pressure gauge reads 60 psi when the low air pressure warning light and buzzer activate. The vehicle is equipped with a 'wig-wag' type warning device. What does this observation indicate?
- AThe low air pressure warning system is malfunctioning.
- BThe air pressure gauge is faulty.
- CThe warning device is functioning correctly.
- DThe vehicle has a severe air leak that needs immediate attention.
Show answer & explanationAnswer & explanation
Correct answer: C. The warning device is functioning correctly.
The low air pressure warning device (light and/or buzzer) must activate at or above 60 psi. If it activates at 60 psi, it is functioning correctly and providing a timely warning of low air pressure, as required by regulations.
Why the other options are wrong
- A. The system is activating at the correct pressure, indicating it is functioning as designed.
- B. The gauge reading is consistent with the warning, suggesting the gauge is likely accurate.
- D. While 60 psi is low, the question specifically asks what the *observation* (warning at 60 psi) indicates about the warning system, not the cause of the low pressure.
Low Air Pressure Warning Activation Point
The air pressure level at which the low air pressure warning light and/or buzzer must activate, indicating a critical drop in system pressure.
- Must activate at or above 60 psi for most commercial vehicles.
- Provides a visual and/or audible warning to the driver.
- Essential safety feature to prevent complete loss of braking.
- Testing this involves pumping the brakes down until the warning activates.
Memory trick: Sixty psi, a warning high, tells you trouble is nigh.