Extruder Motor Just Vibrates, Twitches, Locks System

My Prusi i3 with RAMPS 1.4 has been working well for about 3 years. Suddenly my extruder stopped working and I came to find out that the extruder motor would not run forward or backwards. When called upon, the extruder motor just twitches, or you might say vibrates. I can't move the twitching shaft with my fingers. It seems to be locked up, maybe cycling very quickly between forward and reverse. Once the extruder motor starts twitching, it won't stop until I turn power off to the system. I have tried everything I could think of to resolve this problem.

There is nothing wrong with the motor. For example, the motor runs fine if plugged into the X axis port. I have swapped motor controllers, Arduino Mega 2560 boards, RAMPS 1.4 boards, motors, tested the cable and I simply can't figure it out. The Arduino Mega 2560 replacement board was an R3, and one of two replacement RAMPS 1.4 boards had a place to plug in 12v for a fan that the original did not have, but nothing changed in the way the extruder motor behaved. I don't have any reason to think a Marlin software problem is responsible for the error. I am seriously stuck. Does anyone know what could possibly make the motor twitch like that, and of course, how to fix it? All help will be appreciated.

Edited 2 time(s). Last edit at 05/01/2017 05:04PM by drgrs.

You say the motor runs fine when plugged into x. So what if you plug the x motor into the z driver, will the x motor work or does it just vibrate?

I've tested a motor swap between the extruder port, E01, and X, but I can try Z. I am thinking about changing my mind about this not being a software problem. Both my program file and backup produce the twitching, which seems to make a software, sketch fix unlikely, but impossible is a word I hesitate to use. I can't test the ports tonight, so I will let you know what happens with additional port testing\swapping. Thanks for the response.

Hi guys im new to all this stuff. I had a similer problem and I turned up the pot on the stepper driver and it cured my prublem.

Thanks for the input. Changes to the POT on the back of the E0 controller did not fix the problem. Way back when I first calibrated my machine I had to max out the Y axis POT to stop my prints from tilting, so I have had success with that tweak. No amount of swapping motor plugins changed anything or gave me any more clues than I have at present. I have made a decision to redo the Marlin sketches from scratch. I would rather not, but I have run out of ideas. Before I start from scratch, though, I will reload all of the Marlin sketches and then try my current configuration.h. I just realized the other day that there are a bunch of files involved to run the printer, not just configuration.h and configuration.config. Who knows which one might be corrupted? I will let you guys know how it turns out. I have not tried kicking it yet...

swap a stepper driver before condeming the code.

Grab a multimeter,

You said motor worked if swapped on X. What if you swap X stepper driver to E0? Still twitches?