Inexplicable MINTEMP ERROR on the MK4 with FW 5.1.x
I have a weird problem with my MK4, and I really wonder if I'm the only one. The problem is this error I get more or less every second or third print:
I never had that error message with the firmware versions 4.7 and 5.0, but they started randomly appearing when I tried out 5.1. I downgraded back to 5.0 soem time ago because I also had the nasty Y axis calibration error, but two weeks ago I decided to give 5.1.3 a try. Since then, the issue was back.
I performed the checks on the page the QR code links to and tried some other things, but I could neither find a plausible cause nor a solution for this problem, which really bugs me. I was told by a firmware developer that there's no chance that this is a firmware issue, but guess what went away after I downgraded to 5.0 again?
Now, I have already filed a bug report on Github, so I assume that somebody will check this out sooner or later - but I'd really loave to hear if there is anybody else who has this issue. And I'd be even more grateful for an explanation, if yomebody should have one. 🙂
RE: Inexplicable MINTEMP ERROR on the MK4 with FW 5.1.x
I had exactly the same error at the end of last September (at firmware 5.0.0). I ordered a replacement heatbed thermistor and replaced the part. Since then the error has not appeared again.
RE: Inexplicable MINTEMP ERROR on the MK4 with FW 5.1.x
I guess that this error would show up if the thermistor actually has issues. In my case, though, things do at least look slightly weird. I downgraded to 5.0.0 again yesterday, and the printer has been smelting PETG more or less non-stop since then without a hitch. While being on 5.1.3, I typically had an issue every second or third print or after about an hour - whatever came first. The past 18 hours or so of successful printing also took place with closed enclosure doors. That would have caused the prints to consistently fail after 20-30 minutes before the downgrade.
It might still be a thermistor issue, but if it is, it's a more complex one where something in the new firmware somehow amplifies the issue. I have even been looking through the firmware sources so far, but as far as I can judge it with my lousy C++ skills, there is absolutely nothing there that could explain what I'm witnessing.
RE: Inexplicable MINTEMP ERROR on the MK4 with FW 5.1.x
When I did the replacement then I was just wondering about the fact that there were very detailed instructions for specifically this procedure, at a time when the documentation for maintenance of the printer was not yet very complete. Honi soit ... 😉
RE: Inexplicable MINTEMP ERROR on the MK4 with FW 5.1.x
Thermistors seem to be a much more problematic part than would naively assume, I agree. 🙂
In the meantime, I completed two more prints with the enclosure doors shut and no problems whatsoever. It is certainly possible that I don't have a firmware issue here, but it becomes more implausible with every gram of molten plastic...
RE: Inexplicable MINTEMP ERROR on the MK4 with FW 5.1.x
Ha!
It finally crashed with firmware 5.0 - now it's time to chat with support and get that thermistor replacement. 🙂
RE:
The nozzle and heatbed thermistors are both NTC (Negative Temperature Coefficient) Thermistors.
The minimum temperature means maximum resistance, which can also happen when:
1. the thermistor is incorrectly connected to the board - cold connection - try to shake the the connector for better connection
2. the thermistor wires can be broken or partly broken, which comes in effect when the bed is moving and the wires disconnect.
The relation with the 5.13 could be only a false coincidence. Try to warm up the bed - Control/temperature and try to shake with the cable to see if the temperature will fluctuate.
Having Ohmmeter you could try to measure the resistance at 25°°C it should be about 100KOhm.
RE: Inexplicable MINTEMP ERROR on the MK4 with FW 5.1.x
As I already mentioned, I was able to reproduce the issue with 5.0.0, thus ruling out a firmware issue. I'm waiting for my replacement thermistor now. 🙂
RE: Inexplicable MINTEMP ERROR on the MK4 with FW 5.1.x
I see you helped to solve programmers this issue https://github.com/prusa3d/Prusa-Firmware-Buddy/issues/3757 .
I do not know, if you are aware, this is not related to your issue here. This concerned a wrong message related to the heatbreak thermistor MAXTEMP error.
We will see
RE: Inexplicable MINTEMP ERROR on the MK4 with FW 5.1.x
That is true. I found that location in the code by browsing around, though - it's not related to the actual problem at all.
I had a session with the support people on the chat, and we managed to reproduce the error. According to the support person, the heatbed thermistor is the actual culprit.
RE: Inexplicable MINTEMP ERROR on the MK4 with FW 5.1.x
I have been having the same issue you described, with the same random frequency. It happened 3 times in a row on 16+ hour prints which was very frustrating. I could not reproduce the error, and it went away for about 3 weeks and ~250 hours of prints. Yesterday it came back on 2 prints in a row.
I guess I will chat and get a thermistor replacement?
Thanks for detailing the issue, when I was searching previously I could not find anyone else who was having this issue.
RE: Inexplicable MINTEMP ERROR on the MK4 with FW 5.1.x
I am still having a hard time believing this is an issue with the thermistor, as I can not get it to give a bad reading by moving the wire around at all. We'll see what support says.
@Zappes, have you had the issue since replacing the part?
RE: Inexplicable MINTEMP ERROR on the MK4 with FW 5.1.x
Since I replaced the Thermistor, the problem is 100% gone.
Don‘t be fooled by the cable wiggling being ineffective. I could not trigger the issue that way, either.