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jlg 40ha drive problems

Discussion in 'Other Construction/Demolition Equipment' started by ToddOwen, Jun 25, 2018.

  1. ToddOwen

    ToddOwen Member

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    my jlg 40ha a 1994 i believe is giving me driving problems
    it drives slower than it should and it will continue to drive even slower until it wont drive
    if i shut it down for a few minutes then restart it, it will drive again
    also reverse is worse than forward
    any ideas on where to start
     
  2. ToddOwen

    ToddOwen Member

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    i'm thinking of replacing the joystick controller but its sort of expensive
    anybody have a thought
    is there somewhere that sells rebuilt or used parts that would be a little cheaper
     
  3. willie59

    willie59 Super Moderator

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    Contact Hindley Electronics in Bowling Green Ohio, they can supply the controller for that machine. But first you need to pop the lid at the platform and check the power supply to the controller, should be a yellow wire on terminal 3 of the controller, make sure you're getting good voltage at that terminal with the engine running and operating the controller. It likes to see 12V Nominal, but will work down to about 10 volts. But if it drops to the 8 to 9 volt range it will affect the output of that controller. BTW, don't bother checking output voltage of the controller because you won't make sense of it with a volt meter as the output is pulse width modulation.

    If you have a standard control machine with PQ controllers, you can also swap the drive controller with either tower lift or main boom lift controllers, see if the problem moves to those functions and drive now works proper.
     
  4. ToddOwen

    ToddOwen Member

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    Ok thank you very much for responding
    If I don’t have 10 to 12 volts at terminal 3 is that telling me it is the controller that’s bad
    I’m not sure what pq means
    All my controls are levers that operate the hydraulics except for steering which is a toggle
     
  5. willie59

    willie59 Super Moderator

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    PQ is the brand of the controller, it's the most common controller used by JLG, although over the years they have used OEM, Bertea, Cutler Hammer, a number of brands. Terminal 3 on the controllers is the voltage input to the controller, if you don't have good voltage (12V nom) with engine running and stepping on foot pedal, or if the voltage drops to (roughly) 9 volts or below when you stroke the controller then it will affect controller operation. There's no magic number, it's just most controllers don't like input voltage below 9 or 10 volts. And again, swap the drive controller with either main boom lift controller or swing controller and see how it responds. Many times JLG has modular plugs in the controller harness and you can simply unplug and swap them around without actually removing the controller itself to do the swap.
     
  6. ToddOwen

    ToddOwen Member

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    Thanks again
    I’ll try the swap this weekend
    If the voltage is too low what is the fix for that and where exactly is terminal 3 and is it marked or do I count to find it
     
  7. willie59

    willie59 Super Moderator

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    If it's wired with proper JLG wiring terminal three on the proportional controllers will be a yellow wire. There should be a mark on the terminal strip of the controllers, might be a + mark for terminal 3, and I'm talking about the terminal strip on the controllers themselves, the attached circuit card.
     
  8. ToddOwen

    ToddOwen Member

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    Ok I’m guessing I’ll have to remove the metal housing cover to see everything easily
     
  9. willie59

    willie59 Super Moderator

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    Yeah, you're going to have to pop the lid open at the platform controls