MINTEMP BED error, then self-fixed, but suspiciously at exact same time across prints
My Prusa i3 MK3 was off and dormant for a few months over the holidays and new year. Upon firing it back up to print a simple grease catch for a George Foreman grill in PETG I came across the MINTEMP BED error. I'm comfortable with software and hardware for over 20 years, and something seemed odd about this.
I should mention I've read https://help.prusa3d.com/article/mintemp-error-and-mintemp-bed_2169 already and understand the thermistor can go bad. What's it looks like to me, though, is that the sensor might be failing, or something in the way it communicates the bed temp to the system.
The attached media file below is a very short video where I captured the error occurring. Notice that after the error occurs, the system seems to self-correct and report the bed temp almost immediately - before the print head even returns to a neutral position - displaying "MINTEMP BED fixed". Even stranger to me is that this was the 2nd attempt with this print and it failed at precisely the same point in the print. For experiment's sake, I modified the model slightly and changed the orientation on the build pate and it, too, failed at the same exact place and time for each of the two prints.
Is this a connection issue? I tried wiggling wires while in preheated state, as the guide I linked above suggested. There doesn't seem to be any wire on the whole system I can wiggle that will generate any errors with temperature readings. Before I start ordering parts I wanted to throw this to the community to see if there's experience with this particular behavior.
Here's the error caught in action:
First time posting here (but no stranger to forums) so I tried searching for this error to avoid duplicate/redundant posts. I'm very sorry if I missed something, and I hope someone has a suggestion of where to start. Thank you.
RE: MINTEMP BED error, then self-fixed, but suspiciously at exact same time across prints
Since it is my first time posting, I may not have uploaded my video correctly so I also added to YouTube:
RE: MINTEMP BED error, then self-fixed, but suspiciously at exact same time across prints
temp went to zero, just before mintemp error,
symptom of wire failure on movement
try wiggling the cable bundle and watch LCD
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: MINTEMP BED error, then self-fixed, but suspiciously at exact same time across prints
With the printer preheated I wiggled all wire bundles and can't seem to replicate. Perhaps I'm not being vigorous enough, I'll make some additional attempts.
If we were to go with the idea of a loose connection, how could it happen at exactly the same point of time and location on different attempts to print? Feels too coincidental, though I admit it does sound like a weak wire connection on the surface.
I appreciate the input, thank you!
RE: MINTEMP BED error, then self-fixed, but suspiciously at exact same time across prints
Your issue looks exactly like a problem I had just two weeks ago. You can have a look at the Github issue I opened then and you'll see the similarities for yourself.
Long story short: It was the heatbed thermistor. That bugger can fail in really strange ways, and the cable wiggle trick can't diagnose some of them.