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Jason Guggia
(@jason-guggia)
Member
Side Filament Sensor Issue

Hello Community,

I have been using my Core One(kit) for a month now. All of a sudden, both toolhead and side filament sensors stopped reading the presence of filament for no apparent reason. It now prompts a filament change at the start of every print.

I successful re-calibrated the toolhead sensor, which now works. However, the side sensor remains off regardless if filament is inserted..

What I have done:

  1. Removed the cover over the side IR filament sensor, found the magnetic lever arm movement is free and inserts between the IR filament sensor correctly.
  2. Traced the wiring to the board, found routing correct, free of any chafing and is connected securely into the board.
  3. toggled the filament sensors on and off in settings.

 

Video of Sensor movement

 

Are there any good strategies to troubleshoot this sensor further? I have a lab scope if needed.

Are these IR sensors known for just going out?

 

Any help would be greatly appreciated,

Jason

Posted : 21/09/2025 9:23 pm
hyiger
(@hyiger)
Honorable Member
RE: Side Filament Sensor Issue

I think at this point it’s best to contact Prusa support with your issue. They can help troubleshoot and offer advice. 

Posted : 22/09/2025 3:36 am
hyiger
(@hyiger)
Honorable Member
RE: Side Filament Sensor Issue

Arggg.  Editing doesn’t work. Also, for now as a workaround have you tried disabling the sensor in firmware?

 

Posted : 22/09/2025 3:38 am
Jason Guggia
(@jason-guggia)
Member
Topic starter answered:
RE: Side Filament Sensor Issue

I did! And it still prompted a filament change right before starting the first layer, for some reason. I am going to contact support. 

Posted : 22/09/2025 3:41 am
Jason Guggia
(@jason-guggia)
Member
Topic starter answered:
RE: Side Filament Sensor Issue

Thank you for the advice. I will.

Posted : 22/09/2025 3:41 am
Richard Zimmerman
(@richard-zimmerman)
Active Member
RE: Side Filament Sensor Issue

That sensor is fiddly. You can see what the Prusa is currently reading from that sensor somewhere in the menu (I can't remember where right now, but it will give you real time information as to if it thinks that sensor is open or closed). You have to get the sensor perfectly installed and the magnets exactly in there correctly for it to work right. I had a problem where my cable had an open in it somewhere even though there was no external damage. A chat with Prusa and they shipped me a new one. Then I had a problem where one of the magnets was JUUUUST a little off and it made the sensor work fine while the cover was off and stop working when I put the cover on. Very frustrating to track down.

Posted : 13/10/2025 10:07 pm
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