Practice question

In what order must pneumatic air lines be connected and disconnected when coupling a trailer to a towing vehicle?

  1. When connecting: Yellow (Service) first, then Red (Supply); When disconnecting: Red (Supply) first, then Yellow (Service)
  2. Order does not matter at all
  3. Connect Red first, disconnect Yellow first
  4. Both lines must be connected simultaneously with the engine running at 3,000 RPM

Answer: A — When connecting: Yellow (Service) first, then Red (Supply); When disconnecting: Red (Supply) first, then Yellow (Service)

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