<p>If the error only happens when the printer starts moving it's logical that the issue is in the wire loom that starts to bend and flex once the print starts.</p>
<p>As a quick test and if your comfortable with a little wiring work a temporarily line could be connected directly from the sensor to board. Skipping rewiring the loom until its confirmed to be the issue.</p>
<p>Same logic for the heater wires if it has a connector at the extruder.</p>
<p>Another potential cause for this is if the extruder is already near printing temperature and a new print is started, the printer could think that the temperature shot up way faster then expected even though in reality it was just a bit preheated. If you made any changes to your start G-code, like changing the heating command type or order in witch the extruder/bed is heated, see this stack: <a href="https://3dprinting.stackexchange.com/questions/13353/thermal-runaway-triggers-when-raising-temperature-amid-cooldown?rq=1">Thermal runaway triggers when raising temperature amid cooldown</a>.</p>
<p>Edit:
<a href="https://www.youtube.com/watch?v=JcG7fIcF24k&amp;ab_channel=DaHaiZhu" rel="nofollow noreferrer">This video</a> demonstrates a test to show if Thermal Runaway is enabled. While this setting is not in question here it might be a way to troubleshoot the underling cause for this kind of issue. If the extruder temperatures drop rapidly the same way it does when a print is attempted it might show that the temperature sensor is reading the correct temperature. And thus may indicate a issue with the extruder heating system and not the temperature sensor itself.</p>

CC BY-SA 4.0
2021-08-07T01:29:21.650Z
The wiring was replaced. I showed this to my friend and he pointed out that other people were having the exact same problem with the same thermoster I had, where it is easily damaged/messed up by tension in the connection. 

Here is the thermoster: https://www.amazon.com/Gulfcoast-Robotics-Thermistor-Creality-Printers/dp/B08R3J6GJ3/ref=mp_s_a_1_5?dchild=1&keywords=gulf+coast+robotics+hotend&qid=1628299584&sprefix=gulf+coa&sr=8-5
Twinkle toes
CC BY-SA 4.0
2021-08-07T02:56:16.553Z
@Twinkletoes Apologies I cant yet comment directly on your comment above. So you have tried a total of 3 sensors now? The last one was the glass one? Or are we at two? For each sensor swap was the cable also changed out each time?
Kezat
CC BY-SA 4.0
2021-08-07T14:32:35.770Z
Yeah, the cable was changed. So far I’m at 3 thermosters, two of which were the gulf coast robotics thermosters and the last one being a glass bead thermoster.
Twinkle toes
CC BY-SA 4.0
2021-12-14T22:46:14.130Z
Have you tried a PID tune? I have had problems with my bed where with wrong enough PID values it can't get above 50C and triggers Thermal Runaway. Possibly yours are marginal, and worse when fighting the part cooling fan?
AnotherHowie
CC BY-SA 4.0
2021-08-06T23:33:47.797Z
2021-08-08T22:45:26.870Z
2021-08-08T22:45:26.870Z
Kezat
<p>if the connection to the heaters (nozzle and bed) are not broken and work during printing,
and if the thermistor is reading the correct temperature,
then maybe it is the power supply.</p>
<p>During printing the stepper motors are also consuming energy. If the energy output of the power supply is not enough for the stepper motors and the heaters than the temperatures could go down.</p>
<p>But such an undervoltage situation should also be noticeable in other parts of the printer.</p>
<p>Therefore to be sure that the thermistors are working, try to measure the temperatures with a thermometer. This way you can verify that the temperature change is real.</p>
<p>Another test would be to remove the filament before printing and print without filament. This way the nozzle heater will use much less power, with everything else being the same.</p>
<p>The nozzle heater is temperature controlled. When printing with filament the pushed in filament will cool the nozzle and the heater needs to heat the nozzle up again. With no filament pushed through the nozzle basically stays at the temperature, only cooled by the surrounding air. Therefore much less energy is needed to keep the nozzle at temperature.</p>
<p>If the issue is with the bed heater then move the bed to different positions and wait if the temperature stays the same. If the temperature goes down in a position then the cable for the heater is broken and makes no contact went bend for that position.</p>

CC BY-SA 4.0
2023-07-05T01:54:15.200Z
"print without filament. This way the nozzle heater will use much less power" - Please explain this. The nozzle will be heated no matter what, the printer will not print unless the hotend reaches a set temperature.
agarza
CC BY-SA 4.0
2023-07-05T11:44:47.870Z
I have edited my response with the explanation.
Lars Pötter
CC BY-SA 4.0
2023-07-05T17:31:08.337Z
Thank you, that makes more sense.
agarza
CC BY-SA 4.0
2023-07-04T21:47:26.360Z
2023-07-05T11:44:04.503Z
2023-07-05T11:44:04.503Z
Lars Pötter
<p>I've had this problem on a Prusa MK2s. The print was always at the center of the build plate and that's the location (underneath) of the thermistor. The part was small, the cooling fan was chilling the bed at the same time it was trying to maintain temperature. Moving the part a few centimeters away from the center resolved the problem.</p>
<p>In the case of this PEI coated bed, always centering the print caused the PEI to wear in that area, requiring replacement. The operators were informed to place the build in random, non-centered locations in the future.</p>

CC BY-SA 4.0
2021-08-08T00:38:17.100Z
I have been assuming (perhaps incorrectly) that this is the extruder temperature and not the bed temperature that is dropping/ acting strangely. But I do agree a issue with the bed temperature could also cause a thermal runaway error.
Kezat
CC BY-SA 4.0
2021-08-08T17:08:23.343Z
Yeah, this is definitely an issue with the extruder. I’ve tried printing different models in different locations, but no matter what I do, I still get the same result.
Twinkle toes
CC BY-SA 4.0
2021-08-08T17:15:38.677Z
At the very least, you've eliminated one possible factor. Check your part cooling fan airflow direction, to ensure it's not hitting the hot end.
fred_dot_u
CC BY-SA 4.0
2021-08-08T00:17:43.517Z
2021-08-08T00:17:43.517Z
fred_dot_u
<p>Soo I cleaned my hot end completely took it all apart cleaned it inside and out put it back together and I fix my thermal runaway e1 now my printer runs fine I'd say start there</p>

CC BY-SA 4.0
2022-10-13T22:43:46.163Z
Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer).
Community
CC BY-SA 4.0
2022-10-14T12:13:53.440Z
This sound like there still is a potential problem. You might have a broken wire. During cleaning your heater cartridge or thermistor has made contact again.
0scar
CC BY-SA 4.0
2022-10-13T19:50:22.757Z
2022-10-13T19:50:22.757Z
Michael Lamont
<p>My modded ender three pro had the same issue, it was the shape of the print and the modded fans cooling the print head faster than it could heat, turned the fans down and printed fine.
The moment the fans were full blast the print head temps started dropping straight away</p>

CC BY-SA 4.0
2024-10-18T10:02:51.680Z
2024-10-18T10:03:07.523Z
2024-10-18T10:03:07.523Z
Finlay Maclean
<p>A few weeks ago I got a thermal runaway message on my modded Ender 3 during a print, and I have not been able to get it working since then! I have tried fixing and replacing everything, and I still keep getting the message!</p>
<p>When the printer starts/heats up, the thermistor is able to read the temperature with no problem, but when a print starts, the thermistor starts reading strangely and I get the thermal runaway message! Basically, whenever I start a print the temperature being read slowly drops until it gets to around 20 degrees below the set temperature. I then get the thermal runaway message.</p>
<p>So far, in an attempt to fix it, I have replaced the thermistor twice, the heating element, the wiring was replaced, the firmware and even the entire motherboard! I have no idea how/why I’m still having the message, it just doesn’t make sense.</p>
<p>Also, the thermistor is snuggly attached to the printer.</p>
<p>Please note I’ve tried another thermistor that was glass and had the exact same issues. This lead me to think that this had something to do with the heating element being overwhelmed by something. So, as a test I simply just extruded filament from my nozzle with my fan on to see if that would have the same effect and it didn’t! The temperature stayed up fine. This is leading me to believe that this is some sort of issue with starting a print. Maybe a G-code issue.</p>

CC BY-SA 4.0
2021-08-08T00:28:53.897Z
Approximately how long until you get the thermal runaway message after the first bit of plastic is extruded? Is this time consistent or does it change on every print attempt?
Kezat
CC BY-SA 4.0
2021-08-08T17:04:55.837Z
About 30-45 seconds in. It is very consistant. I have even tried it at different temperatures with different materials and I still get the same results, with the temperature falling by about 20 degrees, then getting the thermal runaway message.
Twinkle toes
CC BY-SA 4.0
2021-08-08T20:49:45.543Z
Disconnect the fans and please try again. If the fan test is done at height, the flow path may be different then when above the bed, e.g. the bed may deflect the cooling flow to the heater block. Also check if the thermistor is correctly inserted and fastened.
0scar
<creality-ender-3><thermistor><thermal-runaway>
Why do I keep getting a thermal runaway message?
Twinkle toes
# Why do I keep getting a thermal runaway message?

(Asked by: username_0 on 2021-08-06)

A few weeks ago I got a thermal runaway message on my modded Ender 3 during a print, and I have not been able to get it working since then! I have tried fixing and replacing everything, and I still keep getting the message!

When the printer starts/heats up, the thermistor is able to read the temperature with no problem, but when a print starts, the thermistor starts reading strangely and I get the thermal runaway message! Basically, whenever I start a print the temperature being read slowly drops until it gets to around 20 degrees below the set temperature. I then get the thermal runaway message.

So far, in an attempt to fix it, I have replaced the thermistor twice, the heating element, the wiring was replaced, the firmware and even the entire motherboard! I have no idea how/why I’m still having the message, it just doesn’t make sense.

Also, the thermistor is snuggly attached to the printer.

Please note I’ve tried another thermistor that was glass and had the exact same issues. This lead me to think that this had something to do with the heating element being overwhelmed by something. So, as a test I simply just extruded filament from my nozzle with my fan on to see if that would have the same effect and it didn’t! The temperature stayed up fine. This is leading me to believe that this is some sort of issue with starting a print. Maybe a G-code issue.

**Tags:** creality-ender-3, thermistor, thermal-runaway
> **Comments:**
> **username_1**: Approximately how long until you get the thermal runaway message after the first bit of plastic is extruded? Is this time consistent or does it change on every print attempt?  
> **username_0**: About 30-45 seconds in. It is very consistant. I have even tried it at different temperatures with different materials and I still get the same results, with the temperature falling by about 20 degrees, then getting the thermal runaway message.  
> **username_2**: Disconnect the fans and please try again. If the fan test is done at height, the flow path may be different then when above the bed, e.g. the bed may deflect the cooling flow to the heater block. Also check if the thermistor is correctly inserted and fastened.  

---

## 5 answers

### Answer by username_1 on 2021-08-06. Score: 1

If the error only happens when the printer starts moving it's logical that the issue is in the wire loom that starts to bend and flex once the print starts.

As a quick test and if your comfortable with a little wiring work a temporarily line could be connected directly from the sensor to board. Skipping rewiring the loom until its confirmed to be the issue.

Same logic for the heater wires if it has a connector at the extruder.

Another potential cause for this is if the extruder is already near printing temperature and a new print is started, the printer could think that the temperature shot up way faster then expected even though in reality it was just a bit preheated. If you made any changes to your start G-code, like changing the heating command type or order in witch the extruder/bed is heated, see this stack: [Thermal runaway triggers when raising temperature amid cooldown](https://3dprinting.stackexchange.com/questions/13353/thermal-runaway-triggers-when-raising-temperature-amid-cooldown?rq=1).

Edit:
[This video](https://www.youtube.com/watch?v=JcG7fIcF24k&ab_channel=DaHaiZhu) demonstrates a test to show if Thermal Runaway is enabled. While this setting is not in question here it might be a way to troubleshoot the underling cause for this kind of issue. If the extruder temperatures drop rapidly the same way it does when a print is attempted it might show that the temperature sensor is reading the correct temperature. And thus may indicate a issue with the extruder heating system and not the temperature sensor itself.

> **Comments:**
> **username_0**: The wiring was replaced. I showed this to my friend and he pointed out that other people were having the exact same problem with the same thermoster I had, where it is easily damaged/messed up by tension in the connection.   Here is the thermoster: https://www.amazon.com/Gulfcoast-Robotics-Thermistor-Creality-Printers/dp/B08R3J6GJ3/ref=mp_s_a_1_5?dchild=1&keywords=gulf+coast+robotics+hotend&qid=1628299584&sprefix=gulf+coa&sr=8-5  
> **username_1**: @Twinkletoes Apologies I cant yet comment directly on your comment above. So you have tried a total of 3 sensors now? The last one was the glass one? Or are we at two? For each sensor swap was the cable also changed out each time?  
> **username_0**: Yeah, the cable was changed. So far I’m at 3 thermosters, two of which were the gulf coast robotics thermosters and the last one being a glass bead thermoster.  
> **username_3**: Have you tried a PID tune? I have had problems with my bed where with wrong enough PID values it can't get above 50C and triggers Thermal Runaway. Possibly yours are marginal, and worse when fighting the part cooling fan?  

---

### Answer by username_4 on 2023-07-04. Score: 1

if the connection to the heaters (nozzle and bed) are not broken and work during printing,
and if the thermistor is reading the correct temperature,
then maybe it is the power supply.

During printing the stepper motors are also consuming energy. If the energy output of the power supply is not enough for the stepper motors and the heaters than the temperatures could go down.

But such an undervoltage situation should also be noticeable in other parts of the printer.

Therefore to be sure that the thermistors are working, try to measure the temperatures with a thermometer. This way you can verify that the temperature change is real.

Another test would be to remove the filament before printing and print without filament. This way the nozzle heater will use much less power, with everything else being the same.

The nozzle heater is temperature controlled. When printing with filament the pushed in filament will cool the nozzle and the heater needs to heat the nozzle up again. With no filament pushed through the nozzle basically stays at the temperature, only cooled by the surrounding air. Therefore much less energy is needed to keep the nozzle at temperature.

If the issue is with the bed heater then move the bed to different positions and wait if the temperature stays the same. If the temperature goes down in a position then the cable for the heater is broken and makes no contact went bend for that position.

> **Comments:**
> **username_5**: "print without filament. This way the nozzle heater will use much less power" - Please explain this. The nozzle will be heated no matter what, the printer will not print unless the hotend reaches a set temperature.  
> **username_4**: I have edited my response with the explanation.  
> **username_5**: Thank you, that makes more sense.  

---

### Answer by username_6 on 2021-08-08. Score: 0

I've had this problem on a Prusa MK2s. The print was always at the center of the build plate and that's the location (underneath) of the thermistor. The part was small, the cooling fan was chilling the bed at the same time it was trying to maintain temperature. Moving the part a few centimeters away from the center resolved the problem.

In the case of this PEI coated bed, always centering the print caused the PEI to wear in that area, requiring replacement. The operators were informed to place the build in random, non-centered locations in the future.

> **Comments:**
> **username_1**: I have been assuming (perhaps incorrectly) that this is the extruder temperature and not the bed temperature that is dropping/ acting strangely. But I do agree a issue with the bed temperature could also cause a thermal runaway error.  
> **username_0**: Yeah, this is definitely an issue with the extruder. I’ve tried printing different models in different locations, but no matter what I do, I still get the same result.  
> **username_6**: At the very least, you've eliminated one possible factor. Check your part cooling fan airflow direction, to ensure it's not hitting the hot end.  

---

### Answer by username_7 on 2022-10-13. Score: 0

Soo I cleaned my hot end completely took it all apart cleaned it inside and out put it back together and I fix my thermal runaway e1 now my printer runs fine I'd say start there

> **Comments:**
> **username_8**: Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer).  
> **username_2**: This sound like there still is a potential problem. You might have a broken wire. During cleaning your heater cartridge or thermistor has made contact again.  

---

### Answer by username_9 on 2024-10-18. Score: 0

My modded ender three pro had the same issue, it was the shape of the print and the modded fans cooling the print head faster than it could heat, turned the fans down and printed fine.
The moment the fans were full blast the print head temps started dropping straight away


---

