BC Transit – Air Brake Course

Combination Truck and Trailer (Secondary Circuit Failure)
A failure in the secondary circuit would render the tractor front brakes inoperative. The
tractor rear brakes (primary) continue to function normally. The trailer does NOT dynamite
because the intact primary circuit now supplies air to the trailer reservoir.
Primary circuit intact and
supplying air to trailer.
Service brakes work
normally.
Two-way check valve moves upward
to protect the primary circuit.
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