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+--- Thread: Park/Trailer valves (/showthread.php?tid=3097)
Park/Trailer valves - flatfoot - 05-12-2018
On a new to me IH 2013 5900i when I set park brake, the trailer charge valve snaps out also. Do I have an issue, never had this on any other trucks I have driven. Non ABS trailer if that makes a difference.
RE: Park/Trailer valves - Chamberpains - 05-12-2018
Nope. They're designed to do that. They don't want you setting one brake without the other.
It's a design that was set in play a long time ago to keep dumbass drivers from setting there tractor brake and not the trailer then hopping out and watching the whole unit roll down a hill away from them. Because the tractor brakes alone weren't enough to hold the whole unit back.
And also if one unit loses air rapidly the other one will lock up to begin slowing the unit down and avoiding a no brake runaway situation. You take your pick on which thought was in mind when they designed it.
RE: Park/Trailer valves - flatfoot - 05-12-2018
Thanks Chamberpains!
Should my 2005 Freightliner do this, as it doesn't?
RE: Park/Trailer valves - Chamberpains - 05-12-2018
Yes. And I can also say that its only been the last couple years that DOT road side checks have been checking for this operation more intensely. NY made me pull my trailer air line while the brakes were released, MD made me bleed the system down by pumping the brake pedal till they both popped and KS made me pull just the tractor brake to see if the trailer followed. And this was in the last 2 years of Inspections. I never had anything but a bleed down test for the low air alarm from 2005 till 2016 so when they started testing this I was quite surprised they did it and surprised my old valve set passed!! Hahaha.
The law is sub section 393.43
Here is a link to an article that goes into some detail about it spawned by a run away truck. The pop out law appears to have been writen in 1988.
http://part380.com/blog/tag/protection-valves-pop-off-test-%C2%A7393-43/
RE: Park/Trailer valves - redbeard - 05-13-2018
Also if the pull knobs are not clearly ledge able, they my write you up. Yellow and red is not good enough.