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How to Replace the Hotend Thermistor

The thermistor is the small sensor that measures the temperature of the heater block. If your printer shows erratic temperatures or a "MINTEMP" / "MAXTEMP" error, the thermistor or its cable is likely damaged.

Safety Warning: Extremely Fragile Component ⚠

The thermistor's wires are very thin and fragile. The glass or metal bulb at the tip is also delicate. Handle with extreme care to avoid damage. Always unplug the printer from the power source before you begin.

Replacement Procedure

  1. Cool Down the Hotend Ensure the hotend is completely cool to the touch.

  2. Disconnect from Mainboard 🔌 Open the electronics case, locate the extruder thermistor connector on the mainboard, and carefully disconnect it.

  3. Remove from Heater Block 🔧

    • The thermistor is a small cartridge inserted into a hole in the heater block, typically held in place by a small screw on its side.
    • Use the appropriate Allen key to loosen this screw very slightly. The goal is not to remove the screw, just to relieve the pressure.
    • Gently pull the old thermistor out of the block. If it's stuck, do not force it. Heating the block slightly might help loosen any plastic residue holding it.

  4. Install the New Thermistor ✨

    • Insert the new thermistor into the hole until it is fully seated.
    • Very carefully tighten the retaining screw. The goal is only to secure it in place, not to crush it. If you overtighten, you will damage the new thermistor.

  5. Connect to Mainboard Route the new cable and plug it into the correct port on the mainboard.

Finalization and Calibrations

Mandatory Calibrations 🔄

Whenever the thermistor is changed, the hotend's thermal behavior changes. * PID Calibration: You must run a new PID calibration so the printer can learn how to maintain a stable temperature with the new sensor. * Thermal Model Calibration (if applicable): This safety calibration must also be re-run.