CDL Air Brakes TestUsing Air BrakesHard
A commercial driver notices that their vehicle's air pressure gauge builds from 85 psi to 125 psi in 30 seconds. The vehicle is a single unit, and the engine is at operating RPM. What does this indicate about the air compressor's recovery rate?
- AThe recovery rate is within acceptable limits for a single vehicle.
- BThis test is only valid for combination vehicles, not single units.
- CThe recovery rate is too slow and needs immediate inspection.
- DThe recovery rate is too fast, indicating a possible gauge malfunction.
Show answer & explanationAnswer & explanation
Correct answer: A. The recovery rate is within acceptable limits for a single vehicle.
For a single commercial vehicle, the air pressure should build from 85 psi to 125 psi within 45 seconds. 30 seconds is well within this acceptable range, indicating a healthy compressor.
Why the other options are wrong
- B. This test is valid and required for both single and combination vehicles.
- C. 30 seconds is faster than the regulatory minimum, meaning it's good, not too slow.
- D. A faster build-up rate is generally a sign of a strong compressor, not a malfunction.
Air Compressor Recovery Rate
A pre-trip inspection test that measures how quickly the air compressor can build air pressure from 85 psi to 125 psi at operating RPM, indicating its health and efficiency.
- Engine at operating RPM.
- Single vehicle: 85 to 125 psi in 45 seconds or less.
- Combination vehicle: 85 to 125 psi in 45 seconds or less.
Memory trick: Recovery Rate: 'Forty-Five Seconds, Fast and Fine!'