What happened?
The printer will display "Extruder thermal runaway: Check the thermistor wiring for potential damage" if the temperature on the nozzle drops by 6 ºC for an extended period of time. This temperature drop would usually not be an issue, but if the heat is not recovered after 20 seconds the error will happen. In this case, the printer will stop the heating and display the message on the screen. The printer then waits for the user to inspect all parts and if needed fix the issue.
Error name: Hotend thermal runaway
Error code: #17204
How to fix it?
The error might indicate some issue with the wiring, either the heater or the thermistor cables are possibly damaged.
A visual inspection
Before breaking out the multimeter you should check the Dwarf board, where the thermistor and heater reside, to ensure that no wires have broken off, or are disconnected.
- the filament is unloaded from the extruder
- the printer is turned OFF and unplugged from electricity
- the hotend and the heatbed are cooled down to ambient temperature
Place an empty Prusament cardboard box approximately to the front center part of the heated. Move the X-axis all the way to the front side of the printer, and move the extruder approximately to the center of the X-axis.
Open the dwarf-cover-door to access the Dwarf board.
Check that all the connectors are secure in their sockets, according to the picture below. Focus on the thermistor and heater cables. Though unlikely, rough shipping or handling could have shaken the heater or thermistor cables loose.
Checking the resistance
The table below describes the correct resistance for each part, as well as what scale you should set your meter to. The hotend thermistor is rated to be 100 kΩ at 25 °C. To be realistic, with a varying temperature between 20 °C and 30 °C, you can expect a wider range of readings (~80-125 kΩ).
There can be micro-fractures in the cable, breaking the connections only at certain positions. Therefore, try to move the cable a bit while doing the measurement and see if the value changes drastically.
Part |
Resistance |
Multimeter scale |
|
Hotend thermistor |
[80 kΩ - 125 kΩ] |
200kΩ |
|
Hotend heater |
[12.3 Ω - 15.1 Ω] |
200Ω |
7 comments
I experienced the thermal runaway error on two consecutive prints at nearly the same spot on the third layer of a print with a fairly large footprint. Filament was Prusament galaxy black with the default 0.2mm speed profile for a 0.6 mm high flow nozzle.
I monitored the print while I tried it the third time, and once it got to the third layer; the reported nozzle temp statrted slowly dropping from 230 down to about 220, flashing orange indicating it was trying to head up the nozzle.
I manually dropped the print speed down to 80% and the temp stated to climb again. I did not get the runaway error. When it started the next layer, I set the speed back up to 100% and got the error again.
I wonder if the heater is simply unable to keep up with the thermal output needed by a 0.6 high flow nozzle when printing a large model with long stretches of infill printed at max speed.
On smaller models it may have time to “catch up” as the print speed drops for perimeters. Interested to see if this is consistent with anybody else’s experience
This totally seems sw related - never had this issue before for a year.
Make resume print available!
We have Prusa XL with 5 extruders, running the latest firmware version 6.2.5 happened also with older versions we experienced this on Extruder 1, extruder 3, Extruder 5.
it does not seems to be a hardware failure rather than a software protection feature that is set too low and without proper margins
This error happens to us quite frequently mainly towards the end of long prints ~after 12 hours and without option to recover the print
requests from prusa:
1. please increase the margins of the error before you completely stop
2. record the last position and enable print recovery
The cable resistances are according specifications and there are 0 chance to get micro-fractures in booth printhead at same time.
If we start to heat-up any of the hotends the machine is restarting and give this error.....