Thermal runaway
What happened?
The printer stopped with a "Thermal Runaway" warning message.
There are two types of Thermal Runaway conditions:
- Thermal Runaway (hotend) - occurs where there is an issue with the hotend maintaining or getting to the temperature requested.
- Bed Thermal Runaway - occurs where there is an issue with the bed maintaining or getting to the temperature requested.
Thermal Runaway warnings are designed to stop the printer if the temperature drops by more than 15 °C for more than 45 seconds. If the temperature doesn't recover within that time, the printer will throw an error and stop.
Why did it happen?
The "Thermal Runaway" warning is a safety feature designed to make sure your printer does not overheat and cause damage to itself or its surroundings. These are most often caused by an environmental factor such as a cold garage or air unintentionally blowing on the hotend or bed, but can also be caused by a thermistor becoming dislodged, becoming defective or bad wiring. Thermal Runaway is a critical feature of your printer that works to prevent catastrophic failures.
NOTE: It is advised that you never leave your printer unattended and have safety measures in place such as smoke detectors and a fire extinguisher at all times.
What do I do next?
A "Thermal Runaway" warning triggers a safety stop, requiring that you switch the power of the 3D printer into the off position. Restarting the 3D printer will clear the error and allow you to restart printing, however it is recommended that you review the steps below to prevent the warning from occurring again.
How can I prevent a Thermal Runaway warning in the future?
Thermal Runaway (hotend - you may see 'Heater_ID: 0' as part of the message)
- Make sure the room temperature is not too low. If the room temperature is 60° F (16 °C) or lower you are more likely to have heating problems. An unheated garage in winter can easily cause thermal runaway as the heater can struggle to maintain temperature and has not been tuned to work at that extreme.
- Visually check the thermistor if it is still securely and correctly installed in the heater block. The whole cartridge should be inside the block, with no part of it sticking out.
- Check the thermistor cable is connected.
- Check that the fan is clear of any damage or debris.
- If you have recently re-assembled your hotend, make sure everything is exactly as instructed. An incorrectly assembled hotend can also cause this error.
Bed thermal runaway
- Make sure the room temperature is not too low. If the room temperature is 60° F (16 °C) or lower you are more likely to have heating problems. An unheated garage in winter can easily cause thermal runaway as the heater can struggle to maintain temperature and has not been tuned to work at that extreme.
- Make sure there are no unintentional sources of cooling, no air blowing on the bed. If the printer is positioned near an air-conditioning or an open window that may be causing excessive air flow.
- Make sure the bed thermistor is still secured.
- Make sure the temperature does not change when moving the bed back and forth. This can help diagnose loose wires.
- Check the thermistor cable is connected.
- If you are printing ABS (or another material requiring high temperatures on the bed) make sure the cooling fan (on the hotend) is off or at a minimum off for the first 10 or more layers.