Sudden random Thermal Runaway errors  

New Member

Hello All, 

I'm a new MK3s+ Owner. I've finished putting my printer together 4 days ago and have been printing constantly since then, mostly to fine tune the issues I've encountered (layer shifts due to belt tension issues, etc.) which I have so far been able to eliminate with ease.

I started a rather large print (12h) in PLA last night and went to sleep when it was about 30 percent complete. In the morning I discovered a Thermal Runaway error, with the print having stopped shortly after my last check. 

I checked the Prusa KB article about Thermal runaway , and had a look at the cables, to see if there was any damage, I've attached a photo:

I also tried printing something else earlier today, and noticed the hotend would drop in temperature when it's supposed to heat up, but it eventually got to the desired temperature. I loaded a file (the test gear pre-loaded on the sd and  got another Thermal runnaway error when starting the print. 

Since I'm fairly new to the 3d printing world, any help would be appreciated. Please let me know if I should include any additional information, as I'm not sure what is and isn't relevant!





Posted : 23/02/2021 8:34 am
New Member

Would also like to mention I am printing from inside my house, which we constantly keep around 22.5 degrees C.

Posted : 23/02/2021 8:53 am
Honorable Member

Welcome to the throng.

The first check for new build teething troubles of this type is the electrical and electronic connections.  Go through all the connectors, pull and remake them in turn; it's easy to be a little too gentle with the plugs at the end of a long build.

If you still have problems, come back and ask again.


Posted : 23/02/2021 8:59 am
New Member


Thanks for the feedback, I will do that later tonight when I have some time. I did a thorough inspection of the extruder, and found filament lodged on and next to the thermistor. After cleanup everything works as expected, so while I'm not discounting any cabling issues, I believe this was the likely culprit.

It seems that my initial layer height was not configured well and it lead to material curling and getting stuck on the extruder assembly in areas I haven't checked before.  I spent my lunch break running the initial layer calibration and I found the sweet spot that makes things stick just perfect.  

Thanks again for the encouragement, and should I discover anything else that might be worthwhile for the greater community, will definitely follow up.

Posted : 23/02/2021 4:20 pm

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