Nozzle Heating Test Failure After Firmware Update to 6.1.2
I haven't used this printer for a while, maybe 6 months and I took the first step of updating the firmware to 5.1.2 to 6.1.2 -
After booting, the firmware seemed to have installed successfully but there was an error message prompting me to run calibration/tests before printing.
I did this, and the nozzle heating test seemed to fail - no error message but just a red X next to this part of the test. I was surprised as this had never happened before, and there were no further error messages or crash logs.
During inspection, the printer, nozzle and wires all look fine and undamaged - and the nozzle easily heats up to 200 degrees during manual temperature operation. 
I ran the test again, and it seems like the nozzle heating test consistently fails when it reaches around 130-135 degrees, and immediately starts cooling down.
I would be grateful for any advice please as I would really like to fix this issue ASAP - my initial thoughts were a faulty firmware install, but I couldn't find any way to re-install the same firmware version to verify this.
RE: Nozzle Heating Test Failure After Firmware Update to 6.1.2
Please provide more details about the printer, because it looks like a custom setup.
Is that a Revo for Mini? Do you use custom heater with higher wattage?
See my GitHub and printables.com for some 3d stuff that you may like.
RE: Nozzle Heating Test Failure After Firmware Update to 6.1.2
Getting the exact same thing on my Mini.
RE: Nozzle Heating Test Failure After Firmware Update to 6.1.2
Okay so I managed to get this "fixed" by restoring printer to factory reset and reflashing FW. not sure, but something must have gone wrong when it was flashed the first time. Mine was on an older version, as updating FW isn't something I do often.
RE: Nozzle Heating Test Failure After Firmware Update to 6.1.2
You can go back to older versions of the firmware: See last section in https://help.prusa3d.com/article/firmware-updating-mini-mini_124784
Having said that, I had something similar happen, and I too thought it was related to a firmware upgrade. For a while I was able to print by simply ignoring the warning but eventually it would fail during prints too. So I ended up replacing both thermistor and heater, and yes, the test now completed successfully so I guess one of them (or both) were indeed defective after all. I wish you luck but don't be surprised if the problem reoccurs and better be prepared to replace heater and/or thermistor
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: Nozzle Heating Test Failure After Firmware Update to 6.1.2
Apologies for being so slow in updating - I fixed the issue eventually, after inspecting various elements and taking multimeter measurements etc. I tried running the test without the silicone sock and it worked first time.. 😴
Perhaps the recent firmware changed the timeout duration for the nozzle heater test, and the sock caused it to heat up slightly too slowly meaning it didn't reach the target temperature in the required time. This would make sense since the nozzle was fine heating up to 215 C and beyond manually via the Tuning menu.
I investigated it very briefly and whilst I couldn't see any references to the nozzle heater test in the firmware changelogs, there were a few references to changes regarding the nozzle and nozzle types so who knows -
Either way, thank you all for the input, hopefully someone with this issue will see this one day for a quick solve.