CDL · Combination vehicles
When the trailer air supply knob is pushed in, what does it do?
Correct answer: It opens the air supply to the trailer.
Answer options
- AIt cuts off the air and applies the trailer's emergency brakes
- BIt sends air to the vehicle's tires
- CIt opens the air supply to the trailer Correct
Why
On newer vehicles the trailer air supply control is a red, eight-sided knob. Pushing it in sends air to the trailer, and pulling it out cuts that air off and applies the trailer's emergency brakes.
About this question
Topic: Combination vehicles License: CDL
Part of these practice sets:
Where it applies: Asked in every state.
Practice the whole set
This question is part of Trailer Air Lines and Coupling (28 questions). Take the full set and check your score.
Practice Trailer Air Lines and CouplingMore questions from Trailer Air Lines and Coupling
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