Which sequence is correct for testing the trailer service brakes?
Correct answer: Make sure air pressure is normal, release the parking brakes, move ahead slowly, then use the hand valve (if equipped) to apply the trailer brakes.
Answer options
- AMake sure air pressure is normal, release the parking brakes, use the hand valve (if equipped) to apply the trailer brakes, then move ahead slowly.
- BUse the hand valve (if equipped) to apply the trailer brakes, release the trailer parking brakes, make sure air pressure is normal, then move ahead slowly.
- CMake sure air pressure is normal, release the parking brakes, move ahead slowly, then use the hand valve (if equipped) to apply the trailer brakes. Correct
Why
Rolling forward slowly before you use the hand valve (trolley valve) on the trailer brakes lets you feel whether they take hold, which shows the trailer brakes are connected and working. That only works once air pressure is normal and the parking brakes are off.
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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