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Why should a driver never disconnect the gladhand lines while the trailer supply pressure is still high without first setting the brakes and following proper uncoupling steps?
- A.Pressurized lines can whip and the trailer emergency brakes will apply suddenly when supply air is lost
- B.The lines contain fuel that will spill
- C.The electrical system will overcharge
- D.The compressor will immediately seize
Correct answer
A. Pressurized lines can whip and the trailer emergency brakes will apply suddenly when supply air is lost
Why
Separating the supply line vents the trailer's emergency circuit and applies its spring brakes, and a charged hose end can move violently. Following the uncoupling sequence, including setting brakes first, keeps that energy release controlled.
Manual topic: Air Brakes - Air Brake System Components · From the Air Brakes practice bank (AB-030).