Prusa error 13211 (Heatbreak Mintemp Error) fires on the MK4 and appears as #31211 on the CORE One, #35211 on the CORE One L, #26211 on the MK4S, #27211 on the MK3.9S, and #21211 on the MK3.9. The firmware detected that the heatbreak thermistor is reporting a temperature below 5°C, a reading that indicates the sensor is disconnected or shorted rather than the heatbreak zone actually being that cold.

What the Error Means

The heatbreak thermistor sits inside the Nextruder and connects to the LoveBoard — the small daughter board mounted within the printhead assembly. This thermistor monitors the thermal boundary between the hot melt zone and the cold feed zone. A sub-5°C reading typically means the sensor’s circuit is open, which the LoveBoard input stage interprets as an extreme low-temperature value. The most common causes are a disconnected thermistor connector on the LoveBoard, a cable that was pinched or damaged during a previous nozzle change, or, less frequently, a failed thermistor bead.

Step-by-Step Fix

1. Power off and cool the printer. Give the hotend at least 10 minutes to cool before touching internal Nextruder components.
2. Access the LoveBoard. Slide off the Nextruder cover — it clips on and requires no tools to remove. The LoveBoard is visible on the side of the Nextruder body.
3. Check the heatbreak thermistor connector. Locate the thermistor cable connector on the LoveBoard and verify it is fully seated. Unplug and firmly reseat it.
4. Inspect the thermistor cable. Trace the cable from the thermistor bead position near the heatbreak to the LoveBoard connector. Look for kinks, frayed insulation, or signs of heat damage.
5. Measure continuity with a multimeter. With the connector unplugged, check resistance across the thermistor leads. At room temperature it should read approximately 85–110 kΩ. An open circuit (infinite resistance) confirms a broken cable or bead.
6. Replace the thermistor if continuity fails. Install a replacement heatbreak thermistor cable, routing it cleanly through the Nextruder assembly.

Parts Required

• Replacement heatbreak thermistor cable (if open circuit is confirmed)
• Digital multimeter

If the connector is secure and the thermistor measures correctly but the error persists, contact Prusa Support at help.prusa3d.com — the LoveBoard itself may have a faulty input circuit.

Frequently asked questions

What does Prusa 13211 mean?

Prusa error 13211 (Heatbreak Mintemp Error) fires on the MK4 and appears as #31211 on the CORE One, #35211 on the CORE One L, #26211 on the MK4S, #27211 on the MK3.9S, and #21211 on the MK3.9. The firmware detected that the heatbreak thermistor is reporting a temperature below 5°C, a reading that indicates the sensor is disconnected or shorted rather than the heatbreak zone actually being that cold.

How do I fix Prusa 13211?

Prusa error 13211 means the heatbreak thermistor dropped below 5°C. Learn how to check the LoveBoard connector and diagnose a disconnected or damaged thermistor.