Air Brake Coach
System failuresQuestion 51 of 116

You push in the red button after coupling, and the gauges do not drop. What does this show?

  1. The compressor is too small
  2. The governor is set too high
  3. The trailer tanks are already full, or the lines are reversed
  4. The trailer brakes are adjusted
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Correct answer: The trailer tanks are already full, or the lines are reversed

A drop in pressure is normal when the empty trailer tanks fill. No drop means they are full or the lines are reversed.

Source: Air Brake Manual: A Guide for Instructors (Government of Alberta, Alberta Transportation, March/April 2012), Module 7: System failures, page 73

Practice system failures

Questions last reviewed: 18 October 2026