Heating Failed
Marlin 3D Printer Firmware
Severity: CriticalWhat Does This Error Mean?
Heating Failed means the hotend or heated bed did not reach the target temperature within the allowed time. This could be a heater problem, a thermistor issue, or the printer simply being in a cold room. Check heater and thermistor connections, and run PID tuning.
Affected Models
- All Marlin-based 3D printers
- Creality Ender series
- Prusa MK3S+
- Anycubic Kobra
- Artillery Sidewinder
- Many others
Common Causes
- Heater cartridge not working or underpowered
- Thermistor reading inaccurate — PID tuning needed
- Very cold ambient temperature slowing heating
- Heater wires loose or corroded
- Wrong heater power configured in firmware
How to Fix It
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Run PID autotune: M303 E0 S200 C8 (for hotend) or M303 E-1 S60 C8 (for bed).
PID tuning optimises the heater control for your specific setup. Send the command via a terminal (OctoPrint, Pronterface). Save with M500.
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Check heater cartridge wiring.
Make sure the heater cartridge wires are firmly connected to the mainboard. Loose connections cause intermittent or no heating.
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Check thermistor wiring.
An inaccurate thermistor reading makes the firmware think the heater is not working. Make sure the thermistor is seated and connected.
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In cold environments: preheat longer or use an enclosure.
If the room is below 15°C, the heater may take longer than the firmware allows. An enclosure helps maintain ambient temperature.
Frequently Asked Questions
What is PID tuning?
PID (Proportional-Integral-Derivative) tuning calibrates how the firmware controls the heater. It learns how your specific heater and thermistor behave and adjusts power delivery to maintain a stable temperature.
Is Heating Failed the same as Thermal Runaway?
No. Heating Failed means the heater could not REACH the target temperature. Thermal Runaway means the temperature is UNCONTROLLED — potentially exceeding limits. Both are safety features but for different scenarios.