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JLG 120HX drive issue

Discussion in 'Other Construction/Demolition Equipment' started by ve6jy, Sep 11, 2017.

  1. ve6jy

    ve6jy Member

    Joined:
    Sep 14, 2013
    Messages:
    5
    Location:
    Edmonton, Alberta
    1996 JLG 120HX sn 229xx

    Has been working well for several years since I acquired it second hand. A swing issue was fixed (thanks to this forum) and no issues until a few days ago. Used around my acreage, I just drove to a location, went up came down and shut it off. A few hours later went to move it and it won't drive. Nothing in forward, reverse, hi/lo creep etc. All other functions are fine. Engine revs up and seems to load a bit. Once got a bit of a jerk motion from the wheels but generally nothing. Doesn't drive from either basket or handheld. Axle lock lights green, everything looks ok. No circuit breakers popped. All wiring and boards are very clean, dry and nothing obvious burnt etc. Pouring over the manuals etc and looking for places to check but thought I'd see if anyone had a similar experience and knew some quick spots to check. Thanks for any help and I'll keep you guys posted as to any progress and test results.

    Thanks, Don
     
  2. laycobeau

    laycobeau Well-Known Member

    Joined:
    Jul 8, 2013
    Messages:
    62
    Occupation:
    Lead electronic technician
    Location:
    Tulsa Ok. beau.bowlan@lei-corp.com
    Do you having steering control? power for steer and travel come from enable
     
  3. ve6jy

    ve6jy Member

    Joined:
    Sep 14, 2013
    Messages:
    5
    Location:
    Edmonton, Alberta
    Yes both front and rear steer are fine.
     
  4. TheFixer

    TheFixer Active Member

    Joined:
    Nov 5, 2015
    Messages:
    27
    Location:
    MI
    I would look at the counter balance valve that controls the brakes. If the engine is loading, than you are probably getting pressure, so I would first find the pressure test quick disconnect and put a gauge on it. You should see probably 3000psi when the drive valve is functioned first to eliminate the valves and the valve controls. If that is good than you probably have to check the pressure on the brake actuators which is controlled by the counter balance valve. You probable need to pull a line at a brake and put in a tee for that test.