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JLG 40H - boom swing does not move in creep mode

Discussion in 'Other Construction/Demolition Equipment' started by motion guru, Aug 21, 2017.

  1. motion guru

    motion guru Member

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    Occupation:
    Machinery Builder
    Location:
    Yacolt, Wa
    I recently bought a JLG 40H and have worked through a number of issues electrical, hydraulic and mechanical and now have everything working with the exception of the swing / rotate function when in creep mode.

    Oddly enough, this function did work when I first got the lift, but now after fixing the basket rotate and boom extend / retract function . . . and after a couple of days of use, the creep speed rotate doesn't move at all. When not in creep speed everything works as it should.

    Where should I start looking? Is the creep speed a hydraulic change in operation or a control level change to the proportional valves? (Or both?)
     
  2. motion guru

    motion guru Member

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    I located a 152 page PDF Service Manual. I was surprised at the lack of a complete hydraulic schematic. Does anyone know of a resource for a schematic for this machine?
     
  3. stone7

    stone7 Well-Known Member

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    Location:
    Midwest
    This google search brings up the 40h manual
    40h https://csapps.jlg.com/OnlineManuals/Manuals/JLG
    I found all 3 manuals at this csapps place.

    I don't know if this will help, but I have found when the swing lever is full on,
    and I press the boom in/out, the swing will speed up. I have the 40ha.

    I think this happens because the over all flow is increased in the combined valve gang.
    And I think this happens because the proportional valve isn't moving fully, because of
    adjustment of the lever control or the valve itself. But I'm only guessing.

    If you find the parts manual, look over your set of valves,
    one is exploded and you can see all the O rings and springs that
    might fail, in the proportional valve. GLTY

    40HA_ControlValves2.gif
     
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  4. motion guru

    motion guru Member

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    Thanks Stone . . . I have put about 20 hours on the lift over the last week. I noticed that when the lift is cold AND I have the boom nearly all the way up (I.e. Minimum drag on the rotate / boom swing axis) that the creep mode works very slowly.

    I'll check voltages going to the he proportional valv and see what I find.
     
  5. TheFixer

    TheFixer Active Member

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    Location:
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    I would check the pressure when you actuate the valve. If it works in not creep mode, than the valve is probably ok, but you need to test the pressure based on the test procedure in the manual to make sure the pressure relief is set right. Once you know that is good, I would look at the procedure for calibrating the controller. The odds are it's bad, maybe going bad, or just needs to be calibrated. The controllers need to be calibrated, or synced, to the valve solenoid since there are variability in the solenoid/valve electrical properties. This procedure should be in the manual.
     
  6. TheFixer

    TheFixer Active Member

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    If you were working on the wiring on the platform controls, than I would check the wires/connector going to the swing controller. The creep switch sends a signal ( I think 12v) to each controller telling ii that it is in creep mode. Maybe a bad connection at that controller.
     
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  7. motion guru

    motion guru Member

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    Thanks Fixer - at this point I am fairly certain that all it needs is a calibration, the pressures are all in order, it appears that the analog signal in creep mode is not high enough to move the valve spool to get flow.

    I need to take the time to go through the manual and understand how to do the calibration . . . I have been trying to beat the rains and focusing on getting my house painted and just running it at normal speed with a deft touch.

    I am almost done painting my house and my only regret at this point is that I didn't buy a 60 ft lift as I could barely reach several places. All in all, I should have bought a lift 20 years ago as this thing has been a huge time saver not to mention far safer than ladders and scaffolds.

    https://photos.app.goo.gl/CeiuPl8bVpMuTfFx2
     
  8. TheFixer

    TheFixer Active Member

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    I hear ya. I started looking at 40's and ended up with a 45. I could really use a 60 but was trying to kèep the weight and machine size down.

    I'm working on a slate roof so it is really needed especially if you are the one man show.
     
  9. motion guru

    motion guru Member

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    I wanted to circle back and let you know what I wound up doing to fix the creep mode on the swing circuit.

    First up, I failed to keep the control console dry and after the first rain, I went to use the lift and I discovered the hard way that the controls have a mind of their own when wet. I stepped on the deadman switch and the lift went straight forward at full speed into a 3 bottom plow and ran the handle of the plow through the radiator . . . $420 later and some minor mods and the cooling system was fixed.

    I dried out the controls and then replaced the pot on the joystick and the drive controls were still flakey and dangerous. In my searching for a new joystick, I came across this unit and ordered it.

    http://www.ebay.com/itm/JLG-Joystic...ING/172864129480?_trksid=p2485497.m4902.l9144

    In the interim, I had to move the lift so I rewired the boom swing joystick to the drive controls and now the drive would not work in creep mode. I noticed the 4 pots on the joystick and after looking at all three joysticks I found that the labels had fallen off nearly all of them except one joystick had a LO label and another had a RMP label.

    So I did some sleuthing and figured out that the pots should be labeled LO, MED, HI, RMP and that Clockwise increased the function while CCW decreased the function. So while in creep mode I experimented with a single turn of one of the two unknown pots and this cause the machine to respond in creep mode. So I labeled that pot MED and then I switched to normal speed and adjusted the HI pot up and down and this affected the top speed for the machine, then I adjusted the RMP pot which changed the slew rate of the command. After all my adjusting, I could control the drive as predictably as ever and as smooth as butter. Then I reconnected it to the swing circuit and this axis now moves reliably and smoothly in both normal and creep modes.

    When the new joystick showed up, I installed it on the swing axis and the old swing joystick is now on the drive control and I adjusted both sets of pots to optimize for smooth control.

    The lift has achieved Nirvana for now . . . just need to get a cover for the control console for when it rains now. Perhaps a BBQ cover or???

    With new radiator and a new joystick and the old joysticks adjusted, I feel like the next person to use it can do so with a lot more confidence.
     
  10. TheFixer

    TheFixer Active Member

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