CDL · Combination vehicles
How do you get air flowing into the trailer's air tanks?
Correct answer: Press in the trailer air supply control knob.
Answer options
- AAttach the glad hand on the service line
- BPress in the trailer air supply control knob Correct
- CPull the trailer air supply knob all the way out
Why
When the trailer air supply control is pushed in, air flows through the emergency (supply) line and fills the trailer tanks. Pulling the control out does the reverse: it cuts off the trailer's air and sets the trailer 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
- What kind of equipment are glad hands?
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- Many combination vehicles use color-coded air lines so the two are not confused. Which colors are typically used?
- In which situation may a parked combination vehicle be held by the trailer hand valve alone?
- As air pressure drops, a tractor protection valve shuts by itself at a level set by its manufacturer. That level usually falls within which range?
- Which sequence is correct for testing the trailer service brakes?
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