Jlg 40h

[77fixer]

I've borrowed a JLG 40H and it is having issues. The owner knows it is less than perfect, but wants to get it into decent shape, so I am trying to help. I am not really familiar with how the hydraulics work on these. The platform and ground controls are all electric with a switch to choose between them.
From the platform everything works ok except Right Rotate. When I picked it up that was pretty slow, now it might work when first started, but then nothing, but it did work.
I used it several hours yesterday with someone bringing sheets of OSB up to me on the roof. We then moved it and I cut most of the rafter tails from the other side of the house. I had it extended out and was working my way back. Retract, then raise/lower as needed. Almost fully retracted and the Lower stopped working.
We went to lunch and came back, same issue. I cut the remaining tails and my buddy was able to bleed the system using what I believe are emergency relief valve (dials behind a door) to get me back to the ground.
The controls work from the Ground control panel, they are all toggle switches vs joysticks at the platform for the Raise/Lower and Rotate Left/Right.
I was out this morning and it seems to be back to working except no right rotate. I want to help get this thing in good shape and am just looking for help.
The owner had another platform control panel, so we pulled the joystick and I swapped each one for the Rotate. I thought maybe the control board was bad. I've checked the junction box at the platform and in the engine compartment. I don't see anything loose/broken/corroded.

Thanks,
Brett

 

[bgaidan]

If the function works on the chassis panel but not in the basket it's most likely a bad joystick or wiring between the basket and the board.

 

[ThePanzerFuhrer]

Yeah wire in the echain. I have one that’s the squirt doesn’t work from the basket. I believe it’s in the wire that runs up to basket. I haven’t had time to Dick with it yet. It’s a good winter project.

 

[77fixer]

So the machine was working to "it's normal". The right rotate is slow, but everything else is working. We used it several hours today and then it started acting up again.

Two things in common both days. The length of time we had run the machine, about 4-5 hrs and that I had been using the auxiliary power to run my skil saw. The aux power does not seem to be what it should, just by the sound of the saw, it is probably low voltage. I'm trying to understand how running the aux generator could affect the function of the pedestal controls. One of the wheel motors leaks pretty good and we also had moved the machine before cutting, both days, so three things in common.
I suppose it could be the wiring between the pedestal and engine compartment, but why does it return to "normal" after many hours? Enough time to completely cool down. When using the joysticks during problem times, sometimes I can hear a change in the way it runs, like it is getting ready to move, but not under any load.
The joystick had a round disk attached that has a dimple. The dimple releases a switch, so that when the joystick is moved slightly, it activates the switch, turning on power, as the joystick moves further it rotates a potentiometer which I believe "throttles" the movement. The ground controls are simple toggle switches.

 

[bgaidan]

All the valves are electronically controlled. If it works as it should from one set of controls, it tells you the valves are good and it's something in the other controls. Heat could be related - heating up the board or a connection and causing intermittent failure.

I'd probe that joystick and see what kind of signal or voltage it's sending out. Next time it fails, figure out how to bypass it and and send a full signal or voltage and see if it works.