Mintemp error during nozzle replacement how to fix?  

This is a new one for the forum, only possible since the last upgrade...

Is it possible to use any of the menu before the error recurs?  If so then there is a gcode that might help: M310 S0 - read about it on https://help.prusa3d.com/article/thermal-model-calibration_382488     If you're not confident with that method come back and I have another that might work - but it's untried.

OR, does the error recur immediately on switch on?

If so go to Prusa Support: Log into your Eshop account, navigate to Company, click Contact Us and 24/7 live Chat is one of the options. This is the quickest way to get live help.

Cheerio,

RE:

You could have broken the hotend thermistor wire, or incorrectly plugged in the thermistor connector on einsy.

When starting the printer it executes a few security checks.

RE: Mintemp error during nozzle replacement how to fix?

After some diagnosis with a multimeter, the thermoresistor has an intermittent error. It doesn’t quite pass continuity all the time, slight movements and it errors out, so there is a break somewhere in the cable. Thought I was being extra careful but still, darn broke it somewhere. I blame the Prusa enclosure access as it’s a PITA to get in there from the front doors alone. I will be doing my own mod and upgrade to make doors on the side(s) in the future. At any rate, I’ll be waiting on the thermoresistor and new hot end assembly for backup in case before I can get back to printing. 
As a note, downgrading to the old firmware solved the stupid beep error but still showed the mintemp on the screen. When you have that error and the hot end reads 0C you cannot do anything from the LCD screen. Nothing responds the click wheel does nothing the X just restarts and shows the same error. At least on 3.10 you can restart without the loud BEEEEP and on 3.12 it will give a loud beep upon boot up. Preferences I guess it’s a nice audible warning you are not going to be using the printer upon startup, but really they gotta do something about that volume it’s loud. 
Thanks for the support as always, thought I just triggered a phantom bug using the wrong nozzle swap but I actually did break the thermoresistor cable. Always nice to believe it’s not hardware and just software! 

RE: Mintemp error during nozzle replacement how to fix?

As the temperature errors ar the most critical, prusa makes sure, you will not do anything before reparing this issue. Especially when this concerns the nozzle. You can hardly overheat the bed but by overheating the nozzle you can get in serious troubles.