Home › CDL Practice Tests › General Knowledge Questions › Question 150
After connecting the service and supply lines, how can you check for a crossed air line hookup?
- A.Crossed lines cannot be detected after hookup
- B.Listen for the radio to change stations
- C.Charge the system and use the trailer hand valve or pedal; the trailer brakes should apply and release normally, and the spring brakes should release when the supply is pushed in
- D.Look only at the color of the tractor frame
Correct answer
C. Charge the system and use the trailer hand valve or pedal; the trailer brakes should apply and release normally, and the spring brakes should release when the supply is pushed in
Why
Crossed lines produce wrong behavior: brakes that will not release, or service brakes with no response. Testing apply and release while still parked turns a dangerous road problem into a simple fix in the yard.
Manual topic: Combination Vehicles - Air Lines · From the General Knowledge practice bank (GK-150).