THERMAL RUNAWAY
Creality 3D Printer
Severity: CriticalWhat Does This Error Mean?
Thermal Runaway means the printer detected that a heater (hotend or bed) is heating uncontrollably or the temperature is not matching expectations. This is a critical safety feature — the printer shuts down to prevent fire. Check the thermistor wiring, heater cartridge, and PID tuning.
Affected Models
- Creality Ender 3
- Creality Ender 3 V2
- Creality Ender 3 S1
- Creality Ender 5
- Creality CR-10
- Creality CR-10S
Common Causes
- Thermistor wire loose or disconnected from the hotend
- Thermistor broken — giving incorrect temperature readings
- Heater cartridge loose in the heater block
- PID tuning incorrect after hardware changes
- Draft or fan blowing on the hotend causing temperature fluctuations
- Firmware thermal runaway protection too sensitive
How to Fix It
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Check the thermistor wires on the hotend.
The thermistor is a small glass bead with thin wires. If the wires are loose, damaged, or disconnected, the printer cannot read the temperature correctly. Make sure the thermistor is seated in the heater block and the screw holds it in place.
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Check that the heater cartridge is tight in the heater block.
A loose heater cartridge heats unevenly and causes temperature swings. Tighten the grub screw that holds the cartridge in the block (gently — do not strip it).
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Run PID autotune to recalibrate the temperature control.
Send M303 E0 S200 C8 via a terminal (Pronterface or OctoPrint). This tunes the PID values for your specific hotend setup. Save with M500.
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Check for drafts blowing on the hotend.
A nearby window, door, or AC vent can cool the hotend and trigger thermal runaway. Use an enclosure or move the printer away from drafts.
Frequently Asked Questions
Is Thermal Runaway dangerous?
The error itself is not dangerous — it is the safety system PREVENTING danger. Without thermal runaway protection, a loose thermistor could cause the heater to run at full power indefinitely, potentially starting a fire.
Should I disable thermal runaway protection?
NEVER disable thermal runaway protection. It exists to prevent fires. Some older Creality firmware had it disabled by default — update to firmware that has it enabled.