Hot End not Heating anymore after Thermal Runaway error
 
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Cogindo Solutions Inc.
(@cogindo-solutions-inc)
New Member
Hot End not Heating anymore after Thermal Runaway error

Hey,

I have an MK3s with the MMU2s and recently did my first overnight print. When I checked this morning I noticed the print has stopped because of a Thermal Runaway. Initially I thought it just got to cold over night where the printer was sitting but when I tried to heat it up this morning the Bed heats up correctly but the Hot End does not heat up at all. I don't think it is the thermostat as it shows readings and goes up a bit as the air around the printer heats up (plus the hot end is not feeling warm at all).

I just recently started really using the printer and up until now it was perfectly fine. Any ideas or hints where I could check for errors why the hot end is not heating up anymore?

Thanks,
Florian

Posted : 01/04/2020 5:05 pm
JPLau001
(@jplau001)
Eminent Member
RE: Hot End not Heating anymore after Thermal Runaway error

Sounds like you have one or more of the following issues:

  • a failed hotend (extruder) heater cartridge.
    Replace the hotend heater cartridge with its attached cable. 
  • break in the cable from the einsy board to the hotend heater cartridge.
    Replace the hotend heater cartridge with its attached cable. 
  • a  hotend heated cartridge cable that has become disconnected at the einsy board side. 
    Ensure that the cable is fully inserted into the extruder heater socket on the einsy.

  • a failed mosfet in the einsy board for the hotend heater cartridge.   
    Replace the einsy board.

You can check the hotend heated cartridge and cable are healthy by disconnecting the extrude heater cable from the einsy board and then using a multimeter in resistance measuring mode. A bad cable or failed heater cartridge will show very high resistance or no connection (an open circuit) between the two conductors of the cable plug at the einsy end. If the extruder heater has failed, buy a new MK3s extruder hotend heater cartridge from the Prusa spare parts section of the Prusa store.   
When installing the replacement cartridge, carefully follow the MK3s extruder assembly and cable management from the hotend  to the einsy to minimize the wear and tear on the replacement cartridge's cable and then rerun the hotend PID tune for the fixed hotend assembly.

You will need to logon to the store via your Prusa account to see the spare parts section of the store to buy a replacement MK3s einsy board or extruder hotend heater 24V 40W cartridge.

Posted : 02/04/2020 6:18 am
JoanTabb
(@joantabb)
Moderator
RE: Hot End not Heating anymore after Thermal Runaway error

Have you checked the fuses on the einsy,

It is possible to replace the wire to the heater if you are careful, If the wire is broken, (which I think is the most likely problem) 
as a temporary repair,  cut the heater wires at the back of the E carriage cable strain relief,  then replace the wires all of the way back to the einsy, solder the joints and insulate with heatshrink...   make sure the joints are supported on the cable strain relief bar, so there is no flexing on the joints. 
this can keep you printing whilst you await spares!

regards Joan

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...
Posted : 02/04/2020 10:54 pm
Cogindo Solutions Inc.
(@cogindo-solutions-inc)
New Member
Topic starter answered:
RE: Hot End not Heating anymore after Thermal Runaway error

Thanks for the feedback. I checked the Heater cable and it seem to be the issue (high resistance on multimeter). So I've ordered a replacement part. Is there a predefined order the two cables from the Heater need to be plugged in into the einsy board or does the order not matter? It does not seem to have any markings to differentiate the two cables.

Posted : 06/04/2020 6:50 pm
JoanTabb
(@joantabb)
Moderator
RE: Hot End not Heating anymore after Thermal Runaway error

Heater is not polarity sensitive

regards Joan

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...
Posted : 06/04/2020 8:33 pm
Cogindo Solutions Inc.
(@cogindo-solutions-inc)
New Member
Topic starter answered:
RE: Hot End not Heating anymore after Thermal Runaway error

Ok perfect. I successful replaced the heater element and at least on a quick self-check as well as on a quick heating of the element everything seem to be back in working order. Lets hope that the new heater element last longer then the old one.

Posted : 06/04/2020 8:34 pm
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