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Blue Service Supply Line Hose

Blue Service Supply Line Hose



 SERVICE AIR LINES.— The service line carries air that is controlled by the foot brake or the trailer hand brake.  Depending  on  how  hard  the  foot  brake  is engaged, the pressure in the service line will similarly change.  The  service  line  is  connected  to  relay  valve(s) on the trailer to apply more or less pressure to the trailer brakes. As pressure increases in the service line, the relay valve opens and sends air pressure from the trailer air tanks to the trailer brake chambers, thus applying the trailer  brakes.

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