Hotend overheating

Came to my M300 printer this morning after a long weekend print and found out the printer when into a thermal runnaway error.

I recently did a full maintenance on the printer cleaning everything and replacing the hotend.
This was my second print after the maintenace and the first one turned out perfect (8h print), this print instead (52h) ran just fine for the first 24h and stopped later.
It’s seems bizzare to me that the cable, heater or thermocouple would stop working suddently.

Measured with a multimeter the resistence of:
heater = 18Ω
thermocouple = 3Ω
are these values correct?

Further informations:

  • I doubt this is a problem but I also have a HEPA cover installed although the fan is not running as I don’t have any spare sockets in that area.
  • Printing with Z-HIPS
  • Noticed during the print that some filament was leaking from the side of the nozzle

Hi @Fra,

the resistance should be around 15-16Ω for heater and 1,6-2Ω for thermocouple (in an ambient temperature). So yes, these parts might be at fault (their approximate lifespan is around 400 working hours).

Just in case - you can run the fan test via menu and check if both fans are operational - if the upper one is not working, the extruder might get overheated during the longer print.

Best regards