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Thermal Runaway Error.  

New Member
Thermal Runaway Error.

HI All.

I have a strange one. My printer keeps heating up starting a print and then throws a thermal runaway error and stops. I have checked the voltage on the RAMBO 12.12 V when heating. No problem with volts then. I have done a conductivity test on the heater element power supply wires, the red ones.

Here is the funny thing. While troubleshooting i noticed the following. I opened the case and removed the case from the frame. When the board is lying down the heating up cycle is consistently fast. When I mount the case back onto the frame., the heating cycle become unstable. It will stop heating. I then gently press on the heating element power plug and sometimes it heats up again.

It looks like a loose connection but conductivity between wires are good. Mind you I get conductivity on both wires from one plus point. Something is either shorting or... loose soldering on rambo?

Posted : 23/10/2017 9:23 am
Noble Member
Re: Thermal Runaway Error.

Hmmm... Could be bad PID settings on the control loop. Have you tried re-runing the PID calibration on the bed?

Does it fail when the nozzle goes over the place where them bed thermistor is attached? Some people have reported that if the fan is active on the lower layers, it blows on the bed and the thermistor picks it up and thinks there is a fault. Moving to another part of the bed seems to help.

Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage or loss. If you solve your problem, please post the solution…

Posted : 24/10/2017 2:51 am
Eminent Member
Re: Thermal Runaway Error.

Hello gents;

I have had the same Bed Thermal Runaway error crop up today during a simple print. I will try the same print again as I did not pay attention to the location of head stopped position.

The wires will be checked prior to running looking for any loose connections.


If you want something different for tomorrow you have to DO something different today. 💡

Posted : 27/10/2017 2:23 am
Eminent Member
Re: Thermal Runaway Error.

Could also be the cooling fan spinning up and cooling down the printbed too much. Try to move the printed part off-center so the cooling fan is not hitting exactly above the thermistor and try again.

Posted : 27/10/2017 10:31 am
Eminent Member
Re: Thermal Runaway Error.

Hello gents, update on the error.

Yes I did check the wires nothing easily visible. I restarted the print and was able to print 4 times over the last few days, same leaf item.

Now today the error popped up again. See attached photo.

You are likely on to something Bariir as my fan shroud is not currently installed due the support structure having some melt damage. The melt damage is old as I have a bad print that was not monitored.

Next step will be to use your suggestion to move the print and to install a fan shroud again. I am in the middle of the upgrade and will reprint all the print head parts in PET and I have covered the heated block with a silicone sock to prevent heat from going where it is not wanted. 😯 😯

To be continued..


(on a side note, how do you keep these images from rotating 90 degrees when you post them?)

If you want something different for tomorrow you have to DO something different today. 💡

Posted : 27/10/2017 10:50 pm
Re: Thermal Runaway Error.

I found that my part fan was overcooling the heatbed , reducing the coolilng helped

if you dont have the duct directing the cooling air at the model, the blast of air will cool the heatbed more than normal'

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 : 28/10/2017 1:58 am
Eminent Member
Re: Thermal Runaway Error.


Hello All;

The issue for me was fixed when I replaced the fan support section and installed the fan shroud. This had been off due to damage to the fan support and the fan shroud sagging so far as to touch the prints.

I had removed the shroud and just recently replaced all the parts. So far so good..



If you want something different for tomorrow you have to DO something different today. 💡

Posted : 30/10/2017 5:38 am
Estimable Member
Re: Thermal Runaway Error.

I fixed my thermal runaway error 😀 - it was a constant pain 😥 😥 😥 and I want to share what I found :idea

First you need the latest firmware version 3.0.12 final

with the new firmware you need to run the PID calibration - this will calibrate the PID so the temperature will remain stable - you need to enter the temperatures a which you will be printing - these calibrations will be stored. In my case I am using mainly PETG so I calibrated for 240 degrees

Next you need to change the filament settings in the Prusa Slicr3r - see end of article
The above article address the problem of too much airflow from the cooling fan causing the hot end to cool down and go into failure. "But new heater block version is bigger and therefore has bigger surface area to get cooled by the print fan"
In the 'filament' section of the Prusa Slicer change the cooling fan settings to: min 15, max 35, bridges 35, disable first 3 layers - this is for PETG only, similar reductions are needed for PLA

When you have made the changer to the filament section of the slicer click the small disk symbol next to the filament type and give your new settings a name - I called mine "PETG 1.75 thermal fix" Saving your setting makes it easy to use in the future and records what your setting where.

I have had no print failures since I made the changes except one time - I then reran the PID calibration again and it fixed the problem. I can only assume the calibration had been lost!

I hope this helps some people - I know how frustrating this can be!!!!!! 😯

Posted : 31/10/2017 5:27 pm
Active Member
Re: Thermal Runaway Error.

I just got this "BED THERMAL RUNAWAY" message. I am printing in PETG and table temp. is set at 90°C.
Like someone suggested it, I just moved the object off the centre of the bed. That solved the problem.
I was printing a small cone with a hole in the middle. Just before the message, temp. was at 82-83 °C.

Posted : 06/11/2017 3:52 pm
New Member
Re: Thermal Runaway Error.


After random thermal runaway errors, I got to the point where I decided to change my thermistor. By doing that I recovered some fine printings, but only for a few prints.
Actually, things became worst with many different failures: under extrusion, cloggings, even Z calibration errors at print starts.

I'll tell you what was happening: after 15 months of use, and once I began to untie the ziptie behind the extruder head, all the wires came to fail: e-motor, pinda probe, fans, thermistor... the ziptie is positionned quite agressively against the wires and doing maintenance here can damage the cables.
I had to change every parts to finally recover a perfectly operationnal printer. It cost me around 70 € with two different shipments as I didn't realize the big picture problem at first.

How to notice the problem if you are in the same situation: check the wires by moving them a bit directly behind the extrusion head.
Hope it will help!

Posted : 18/03/2018 10:26 pm
Active Member
Re: Thermal Runaway Error.

Even tho my contacts were not solid enough (after replacing thermistor and heater) I found a better way to compensate for the fan induced error:

Turn the fan to 255 in Settings > Temperature, then do the PID calibration with the fan on. Et voila, no need to adjust the slic3r profiles or firmware.

Posted : 07/08/2018 5:34 pm