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MMU3 is on but not responding to anything  

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Nodak7
(@nodak7)
Eminent Member
MMU3 is on but not responding to anything

Recently I was printing with my MMU3 and a segment of filament jammed between the selector and the filament entry. It took a bit of fiddling to get it unjammed and cleaned out. Anyway after I got it all back together and the selector was not working. I thought it was a bad selector motor so I replaced it. I put it all back together and still nothing is working. The lights come on for the filament indicators so I know the unit has power but other than that nothing else seems to be working. The 3 switches for moving the selector and unloading are not working. Can anyone give me a suggestion on how to troubleshoot it?

Posted : 19/12/2025 6:28 pm
mnentwig
(@mnentwig)
Reputable Member
RE: MMU3 is on but not responding to anything

Check the FINDA sensor (the later versions have a LED and it should be ON without filament).

If it's detecting filament, the MMU will play dead after a short blink code sequence. I had similar behavior once caused by jammed debris in the sensor assembly.

Posted : 19/12/2025 6:56 pm
Nodak7
(@nodak7)
Eminent Member
Topic starter answered:
RE: MMU3 is on but not responding to anything

Thanks for your response! Yes the FINDA light is coming on. I checked the calibration and it seemed to work properly. When i turn the printer on there is other than the lights there is no sign of life. I tried to move the finda using the buttons and no response. 

Posted : 19/12/2025 7:29 pm
Nodak7
(@nodak7)
Eminent Member
Topic starter answered:
RE: MMU3 is on but not responding to anything

Thanks again for your response! I recalibrated the FINDA and restarted the printer and now it appears to be working! Thanks I think you put me on the right track!

Posted : 19/12/2025 8:11 pm
mnentwig
(@mnentwig)
Reputable Member
RE: MMU3 is on but not responding to anything

The lack of even an error code for misbehaving hardware is not good.

Posted : 19/12/2025 9:11 pm
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