Air Break Practice Test

Results

#1. On a tractor-trailer, if the supply and service lines to the trailer are cross-connected, what may happen?

The service brakes will not work.

The trailer parking brakes may not release.

The tractor may lose compressed air.

All of the above may happen.

If you cross-connect the air lines, supply air will be sent to the trailer service line instead of the trailer air tanks. Tank air will not be available to release the trailer spring brakes (parking brakes). And when you press the brake pedal, service air won’t flow to the trailer brake chambers, so the service brakes won’t work either.