Which component of the air brake system cuts-in at 100 psi to allow the air compressor to run?
Answer: B
Air compressor governor
The air compressor governor will cut-in to allow pressure to build at 100 psi and cut-off to stop pressure between 120 and 140 psi
All choices
- AAir pressure relief valve
- BAir compressor governor
- CTractor-protection valve
Why the other answers are wrong
A. Air pressure relief valve
Choice A is wrong because the air pressure relief valve releases excess pressure, it does not control compressor cut-in.
C. Tractor-protection valve
Choice C is wrong because the tractor-protection valve controls air flow to the trailer, not compressor operation.
CDL Air Brakes Test Info
Questions on Exam
25
Passing Score
80%
Time Limit
Typically 30 minutes; varies by testing location
The Air Brakes test content is federally standardized, so this question applies in every state. Age limits, fees, and testing procedures do vary — check your state's CDL requirements.
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More CDL Air Brakes Practice Questions
- The safety valve is set automatically when pressure is:
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