CDL Combination Vehicles TestCombination Vehicle Air BrakesHard
During a pre-trip inspection, you find that the air compressor governor on your combination vehicle cuts out at 110 psi. What does this indicate, and what action should you take?
- AThe cut-out pressure is too low; the governor needs adjustment or repair.
- BThe compressor is faulty, not the governor; replace the compressor.
- CThis is within the normal operating range; continue driving.
- DThe cut-out pressure is too high; the governor needs adjustment or repair.
Show answer & explanationAnswer & explanation
Correct answer: A. The cut-out pressure is too low; the governor needs adjustment or repair.
The air compressor governor typically cuts out between 120-140 psi. A cut-out pressure of 110 psi is too low. This means the system will not build enough maximum pressure for safe operation and reserve capacity, indicating that the governor needs adjustment or repair to ensure proper system pressure.
Why the other options are wrong
- B. The governor controls the cut-out pressure. If the pressure is incorrect, the governor is likely the component at fault, not necessarily the compressor itself (which might be working but being told to stop too early).
- C. 110 psi is below the normal cut-out range, which is typically 120-140 psi.
- D. A cut-out pressure of 110 psi is too low, not too high.
Air Compressor Governor Cut-Out Pressure
The pressure at which the air compressor governor stops the compressor from pumping air into the system, typically between 120 and 140 psi, to prevent over-pressurization and maintain system integrity.
- Normal range: 120-140 psi.
- Too low: insufficient air reserve.
- Too high: risk of component damage.
- Governed by the air compressor governor.
Memory trick: Governor Guides Gauge's Goal.