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Two ride height control valves on one trailer tandem?? cannot agree with each other?

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by ichudov, Dec 3, 2017.

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  1. Dec 3, 2017 #1
    ichudov

    ichudov Heavy Load Member

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    I have a step deck semi trailer. This trailer happens to have TWO ride height control valves, one for right side and one for left side of the trailer tandem.

    The problem is that it is very difficult to get them to agree with one another. Either one valve makes one side higher and holds all the weight , or another valve does that. The result is that one side air bags are fully inflated and the other side is deflated. It is hard to get them to hold one height.

    I also must note that one valve is in relatively new condition, whereas the other valve is quite old and dilapidated, and perhaps does not hold its dead band, or some such.

    Does anyone have any experience adjusting twin ride height valves?
     
    ichudov, Dec 3, 2017
    ichudov, Dec 3, 2017
    #1
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  3. Dec 3, 2017 #2
    swaan

    swaan Road Train Member

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    Yeah .

    Take one off and just use one valve.
    Plumb all four bags to one valve.

    Ive never seen 2 valves on a trailer ever.
    Some KW tractors with 8 bag had 2 valves but most people reverted them back to 1 valve.

    Save yourself the aggravation and just plumb it for a single control valve.
     
    swaan, Dec 3, 2017
    swaan, Dec 3, 2017
    #2
    Ozdriver, magoo68, Heavyd and 3 others Thank this.
  4. Dec 3, 2017 #3
    ichudov

    ichudov Heavy Load Member

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    Swaan, not that I know anything... I was going to do the same thing as you suggested, change to single valve, but I looked at some HCV manuals online, and they say DO NOT CHANGE A DUAL SETUP TO SINGLE VALVE.

    Not sure why they say so. Maybe the suspension is in some way meant to be used with dual valves?

    They are for sure a PITA. Maybe it gets better when the trailer is loaded?
     
    ichudov, Dec 3, 2017
    ichudov, Dec 3, 2017
    #3
    Ozdriver Thanks this.
  5. Dec 3, 2017 #4
    swaan

    swaan Road Train Member

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    What kind of trailer and what brand of air ride under It?
     
    swaan, Dec 3, 2017
    swaan, Dec 3, 2017
    #4
  7. Dec 3, 2017 #5
    ichudov

    ichudov Heavy Load Member

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    The trailer is Dynaweld IIRC, not sure what brand air ride though. The valves look like Haldex.
     
    ichudov, Dec 3, 2017
    ichudov, Dec 3, 2017
    #5
  8. Dec 3, 2017 #6
    swaan

    swaan Road Train Member

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    Hmmmm
    I wouldn't be afraid to revert back to 1 valve.
    You will be constantly tweaking those valves to make the trailer sit straight. They have to be perfect or they fight each other and if your OCD like me it will drive you crazy. Lol
     
    swaan, Dec 3, 2017
    swaan, Dec 3, 2017
    #6
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  9. Dec 3, 2017 #7
    ichudov

    ichudov Heavy Load Member

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    They drive ME crazy that is for sure!!!!!
     
    ichudov, Dec 3, 2017
    ichudov, Dec 3, 2017
    #7
  10. Dec 4, 2017 #8
    Heavyd

    Heavyd Road Train Member

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    I would recommend to call the trailer manufacture and ask them about the dual leveling valve set up. Ask them why it needs two and if you can replumb to one because of the problems you are having. Trucks use to have this too for a while and it just didn't work. Like you said, they just keep fighting each other and never really equaled out anyway. Unless the manufacture has some legitimate reason to run with dual valve, I would also revert to using only one.
     
    Heavyd, Dec 4, 2017
    Heavyd, Dec 4, 2017
    #8
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  11. Dec 4, 2017 #9
    BoxCarKidd

    BoxCarKidd Road Train Member

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    Worked on some duel systems. At least some were Kentucky Trailers and all were double deck with a lot of high weight when loaded. Suspensions were Newway. The company required us to maintain as original.
    Tips if in doubt replace the valve-valves. Do not be to quick to adjust. We could drive around the block one way and trailer would lean one way. Drive around the block the other way and the trailer would lean the other way. If it was close leave it alone and only adjust based on leaning one way more often than not.
    We were told the purpose was that the suspension could compensate in a turn. Unless it is a very long turn I do not thank the suspension can respond fast enough to matter. I did suck up a seat cushion on a cloverleaf with one of those one time. If is amazing how far that type suspension can allow a trailer to lean even at slow speed. I was afraid to speed up or slow down. Went to the outside slow and steady, maybe the suspension saved me?
    On a flatbed I believe it unquestionably worthless.
     
    BoxCarKidd, Dec 4, 2017
    BoxCarKidd, Dec 4, 2017
    #9
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  12. Dec 4, 2017 #10
    ichudov

    ichudov Heavy Load Member

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    OK, just a little followup. I went to Indiana today to pick up two CNC machines. They were loaded badly (unbalanced) and the left side was much heavier than the right side. It looked ridiculous before air was let into the trailer. But the dual valves compensated it pretty nicely. Maybe I will make an extra effort to fix this, change the older valve and readjust.

    I still have them sitting on my trailer, I will take some pictures tomorrow.
     
    ichudov, Dec 4, 2017
    ichudov, Dec 4, 2017
    #10
    OLDSKOOLERnWV Thanks this.
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