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Down pressure a bit wonky

Discussion in 'Sno-Way Discussion' started by Peterbilt, Dec 12, 2008.

  1. Peterbilt

    Peterbilt Senior Member
    from IA.
    Messages: 745

    Put plow on today.

    I hit the down pressure button, plow lights tilt back then engage the truck mount. everything is going normal. then.....

    Then pump keeps surging, lifting front end up and down. Turn off DP then it stops. Turn on again and its starts surging.

    We assume its low on fluid... Nope, looks good.

    Any Ideas. Its the first time in 2 years we have had a problem. Its a 22 series. We need the down pressure. lol

    J.
     
  2. hydro_37

    hydro_37 PlowSite Veteran
    from iowa
    Messages: 3,790

    Sounds to me like it is just cycling. Mine clicks alot and it is normal.
     
  3. toby4492

    toby4492 2000 Club Member
    Messages: 2,513

    I would agree that it sounds like it is cycling by your description. How often does it do this if in a static down position over a one minute period?
     
  4. Peterbilt

    Peterbilt Senior Member
    from IA.
    Messages: 745

    Alot. about every 2 to 3 seconds maybe 5 seconds. We didn't time it. It did something it doesn't normally do. We checked the simple things, and I asked the question before we tore into it.

    J.
     
  5. toby4492

    toby4492 2000 Club Member
    Messages: 2,513

    Try cycling the plow up down left right etc for a minute or so just in case it is nothing more than some air in the system or a small piece of debris hung up somewhere. Fully extend all cylinders several times and drop the blade in the straight position and recheck the oil level. Run the DP again and lets see if there is any change.

    If there is no change it tells me that it is not properly holding pressure. If that is the case there are a couple of things that we can have you check.
     
  6. Peterbilt

    Peterbilt Senior Member
    from IA.
    Messages: 745

    Will do. Thanks Toby.

    J.
     
  7. oldmankent

    oldmankent PlowSite.com Addict
    Messages: 1,318

    I'm getting a new pressure switch for mine next week. I can watch my voltmeter cycle continually while I have the down pressure on. If your truck is sitting still the down pressure should hold pressure for more than 5 seconds before cycling on again.
     
  8. basher

    basher PlowSite Fanatic
    from 19707
    Messages: 8,992

    Have it tested, pressure switches are not the only culprit.
    It could also be a tried down pressure relief valve or a worn lift cylinder.
    Installing a pressure gage on the dp hose and checking the constant pressure could be advisable if you have not already. As the units age the spring in the DP pressure relief get tired and do not hold enough pressure to allow the Dp to hold enough pressure to satisfy the DP switch.

    Also a worn lift cylinder packing will allow pressure to pass though once again not allowing enough pressure to build to silence the PR switch. Does your unit drift down at any point of the lift range?