CDL Combination Vehicles TestCombination Vehicle Air BrakesEasy
During a pre-trip inspection of a combination vehicle's air brake system, you notice that the air pressure builds from 85 psi to 100 psi in 30 seconds. What action should you take?
- AThis indicates a healthy system; continue with the inspection.
- BThis indicates a problem; the air pressure rise is too slow.
- CThis indicates a problem; the air pressure rise is too fast.
- DThis pressure range is acceptable, but the time is too short.
Show answer & explanationAnswer & explanation
Correct answer: B. This indicates a problem; the air pressure rise is too slow.
The air pressure buildup rate is a critical indicator of the air compressor's health and system integrity. For combination vehicles, the air pressure should rise from 85 psi to 100 psi in no more than 45 seconds.
Why the other options are wrong
- A. The pressure rise is too slow, indicating a potential issue with the air compressor or system leaks.
- C. A faster rise time would generally indicate a more efficient compressor, not a problem.
- D. The pressure range is correct, but the time of 30 seconds is actually good, not too short to be a problem.
Air Brake Pressure Build-Up Test (Combination Vehicle)
A pre-trip inspection test to ensure the air compressor can quickly build and maintain sufficient air pressure for safe operation of a combination vehicle's air brakes.
- Air pressure should build from 85 psi to 100 psi in 45 seconds or less.
- Performed with the engine at operating RPM.
- Indicates compressor health and leak integrity.
Memory trick: Pressure Power Pushes Quickly.