Prusa 3D Printer Error Code 3: How to Fix It

Q: What causes Prusa Error Code 3 MINTEMP hotend?

The most common causes are a thermistor that has slipped out of the heater block, a broken wire in the fragile thermistor cable (often from repeated movement during printing), a loose connector at the control board, or a thermistor that has failed internally. Less commonly, a damaged control board thermistor input can also trigger this error.

Q: Can I keep printing if I get Error Code 3 on my Prusa?

No. Error Code 3 causes an immediate print halt and you should not attempt to override it. The printer cannot safely regulate hotend temperature without a working thermistor, which could cause uncontrolled overheating, fire, or damage to the hotend and printer. Always resolve the error before resuming printing.

Q: How do I know if my Prusa thermistor needs replacing?

Use a multimeter set to measure resistance (Ohms). Disconnect the thermistor from the board and measure across its two pins. At room temperature, a healthy NTC 100k thermistor reads approximately 100,000 Ohms (100kΩ). A reading of 0 (short) or infinite resistance (open/broken circuit) means the thermistor must be replaced. You can also flex the thermistor cable while watching the temperature on the LCD — a flickering or erratic reading points to a broken wire.

Q: How much does a replacement Prusa hotend thermistor cost?

Replacement NTC 100k thermistors compatible with Prusa printers are generally inexpensive, typically ranging from $5 to $20 depending on the source and whether you buy a single thermistor or a kit. Prusa's own online shop sells model-specific replacement thermistors, and compatible third-party options are widely available. Always verify compatibility with your specific Prusa model (MK3S+, MK4, Mini, etc.) before purchasing.

Q: Will Error Code 3 go away on its own or after a reboot?

If the thermistor wire has an intermittent break, the error might not appear immediately after a cold reboot, but it will almost certainly return once printing starts and the cable begins flexing with extruder movement. This is a hardware issue that does not resolve itself. Even if a reboot temporarily clears the error, you should inspect and test the thermistor and wiring before trusting the printer for a long unattended print.

Abstract

Prusa Error Code 3 is a MINTEMP (minimum temperature) error on the hotend, meaning the printer's control board is reading a temperature that is too low — often 0°C or a clearly impossible value — from the hotend thermistor. This usually points to a disconnected, damaged, or failed thermistor, a broken wire in the hotend cable bundle, or a faulty connection at the control board. Because the printer cannot safely heat the hotend without reliable temperature feedback, it immediately halts to prevent fire or damage.