My throttle control stepper motor is on the fritz in my JD 790 elc. It will cycle back and forth from idle to full throttle constantly until you mash the buttons to make it stop. Then to throttle up you have to press any other button and then hit idle quickly to throttle it up in increments. The bad part of that is your left in idle postion and everything is slow ( track speed) . Before I throw a new on on there for 500 dollars... can it be calibrated? Or is it the computer controling the motor? Or something else? Any sugestions would be appreciated. Ty
Im working on a similar issue my stepper motor on my hitachi 200-3 is not responding except rarely and the fuel cutoff motor is not letting the motor run so im going to check all the wiring to them next i had dr zx on the machine and the engine rpm doesnt apear to change when loading the machine but you can hear the engine loading a bit as you lift the machine so the rpm should be dropping does anyone have a full wiring schematic for the machine?
Sounds like water/corrosion/moisture in the control panel or maybe wiring harness worn through and shorting... check under the cab floorboards.
The control panel behind the seat?
oh i see i can test the stepper motors for function with an led
As said, corrosion, and check grounds, and a really long haired one, had a blown diode or 3 in the alt on our 892e and it was putting ac in the system and making things act wierd, stepper was not as erratic as yours but close.
Many times on JD/Hitachi Excavators I've seen the harness within a few feet of the EC motor damaged causing it to work erratically. Usually from hyd fluid leaking on the harness for long periods or sticks poking up through the belly. It's the 1st thing I check on these calls anymore.