From: Recovry4x4@aol.com
Date: Sat Feb 19 2005 - 19:43:15 PST
Patrick, better have a closer look at those hoses. The red hose is supposed
to be emergency and has air all the time. The yellow is service air and only
has air under brake application. Both lines go through a relay valve. Basically
the relay valve is responsible for maintaining a supply of air in the trailer
air tank. Secondly it applies the brakes if the brake lines were ripped or
another significant loss of air. It's third function is receiving the air signal
from the towing vehicle and applying the brakes with air from the trailer
storage tank. The lines may have been repainted incorrectly too. I know if I disco
the emergency air on mine, the relay valve senses that and locks up the
brakes. The only way I can then unlock them is to bleed off the air in the trailer
tank until the relay valve resets. Make sure your truck has adequate air
pressure and that the petcock is closed on the trailer tank and try it with the
lines swapped. If you still have problems I'll crawl under one of mine and
identify which line goes where on the realy valve and get the info posted. If you do
lock up the brakes, drain the air from the trailer tank to release them.
Kenny
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