CDL Combination Vehicles TestCombination Vehicle Air BrakesMedium
Which of the following conditions would indicate a potential problem with the 'air compressor' during a pre-trip inspection of a combination vehicle?
- AExcessive oil leakage around the compressor unit.
- BThe air dryer purges air every 3 to 5 minutes.
- CThe air compressor builds pressure from 85 psi to 100 psi in 20 seconds.
- DThe air compressor governor cuts out at 125 psi.
Show answer & explanationAnswer & explanation
Correct answer: A. Excessive oil leakage around the compressor unit.
Excessive oil leakage around the air compressor unit indicates a seal failure or other internal problem, which could lead to compressor failure or contamination of the air brake system with oil.
Why the other options are wrong
- B. The air dryer purging air every few minutes is normal operation, indicating it's removing moisture from the system.
- C. Building pressure from 85 to 100 psi in 20 seconds is generally acceptable for a combination vehicle, indicating proper compressor function.
- D. A governor cut-out pressure of 125 psi is within the normal operating range (typically 100-125 psi).
Air Compressor Malfunction Signs
Signs of a malfunctioning air compressor include excessive oil leakage, unusual noises, inability to build or maintain pressure, or the governor failing to cut in/out at correct pressures.
- Oil leakage indicates seal issues.
- Compressor is vital for air brake function.
- Failure can lead to brake loss.
Memory trick: Oil leaks mean the 'Compressor' is 'Compromised'.