Thermal Runaway

I have been getting an error about thermal runaway error please reboot this started after my firmware update also it seems to be on every print any suggestions. From what I see on my LCD before it craps out the temp is just randomly dropping with fan speeds that worked on the old firmware.
How much is the temp falling?
Best bet is to change the values in the firmware. I think they set it too close.
Google it.

But I had a similar problem on another printer and it turned out to be the hotend wiring was frayed and it was causing the problem.
So if there's no "mechanical" problems, change the firmware.
I think you'll find it is pretty common with stock Marlin.
Just an update I didn't find any frayed wires but didn't unplug my hotend wires and plug them back in so far my temps are holding with normal fan speed. However I did mange to break my one of the wires on my LED lights where do I get replacement LEDs from?
That's a big drop.
Did you consider the fan shroud? They do eventually melt a little and may be blowing on the hotend instead of below it.


Staff member
If you are using an E3D, make sure to use the silicone sock that came with installed. That will help regulate the temperature. Also, I would suggest lowering your fan speeds. And not turning it on to high while on the first couple layers.
Good call on the silicone sock my friend had to help me re-build my E3D and we forgot to put the silicone sock back on. I"m sure that is causing a lot of the issue but for now I will just keep my fan speed down because it looks like I would have to take my project cooler fan off and the front of my E3D assembly to be able to get the sock on. Which would also mean re-leveling my bltouch. I've noticed its much more of a challenge to get the bed leveled just right using a volcano.
I ended up breaking down and installing my silicone sock and a replacement fan shroud I printed on my Ultimaker 3 extended with dissoluble PVA for support. My old fan shroud was in ok condition but a bit worn. I was able to do a test of my famous CR-10 cat with no issue so I think it was just the lack of a sock causing my thermal issues. Unfortunately I will be out of town this weekend so won't be able to do some prints. All and all the new firmware seems to be a huge improvement in terms of leveling and I was dealing with the thermal issue with my fan turned down even with no sock installed.