CDL Air Brakes TestAir Brake System PartsEasy
A driver is performing a pre-trip inspection on a commercial vehicle equipped with an air brake system. They notice that the air compressor builds air pressure from 85 psi to 125 psi in 40 seconds. What does this indicate about the air compressor's performance?
- AThe air compressor has a leak in the discharge line.
- BThe air compressor is building pressure too quickly, indicating a governor malfunction.
- CThe air compressor is building pressure too slowly and requires maintenance.
- DThe air compressor is building pressure within the acceptable range.
Show answer & explanationAnswer & explanation
Correct answer: D. The air compressor is building pressure within the acceptable range.
For a properly functioning air brake system, the air compressor should be capable of building air pressure from 85 psi to 125 psi within 45 seconds for dual air systems. Building pressure in 40 seconds falls within this acceptable range.
Why the other options are wrong
- A. A leak would cause the air compressor to build pressure more slowly or not hold pressure, not necessarily faster.
- B. Building pressure quickly is generally good; a governor malfunction would typically cause pressure to build too high or not at all.
- C. Building pressure in 40 seconds is faster than the minimum requirement, not too slow.
Air Compressor Build-Up Rate
The rate at which the air compressor increases air pressure in the air tanks, which must meet minimum standards during inspection.
- Must build from 85 to 125 psi within 45 seconds (dual air systems).
- Must build from 50 to 90 psi within 3 minutes (single air systems).
- Tested during pre-trip inspection to ensure system health.
Memory trick: Pressure Up, Time Is Right.