How to Fix Prusa MINTEMP Error: 3 Simple Steps to Save Your Print
If you just turned on your Prusa i3 MK3S+ (or woke up to a halted overnight print) and saw a flashing red screen, you need to know how to fix Prusa MINTEMP error fast.
This specific notification is a hard-coded safety feature in the Prusa firmware. It means the printer’s Einsy RAMBo motherboard is reading a temperature of 0°C (or below 15°C ambient) from either the hotend or the heated bed, triggering an emergency halt to prevent the printer from indefinitely sending power to a dead sensor.
Quick Answer: To fix Prusa MINTEMP error, you must first verify your room temperature is above 15°C (59°F). If the room is warm, the error is caused by a broken thermistor wire. You must check the LCD to see if the bed or the hotend reads 0°C, then replace the damaged thermistor to restore normal operation.
In this guide, we will break down the two main causes of this error, how to test your wiring, and the exact replacement parts you need to get your farm back online.
Key Takeaways
- The MINTEMP error is a safety mechanism triggered by a temperature reading below 15°C.
- A cold garage or basement will trigger this error even if the printer’s hardware is perfectly fine.
- If the room is warm but the LCD reads 0°C, the fragile glass bead thermistor wire has snapped and must be replaced.
What Causes the MINTEMP Error?
This error code is your machine’s way of saying: “I cannot read the temperature, so I am cutting power to prevent a fire hazard.”
There are two variations of this error:
- MINTEMP: This indicates the hotend thermistor is failing or too cold.
- MINTEMP BED: This indicates the heated bed thermistor is failing or too cold.
When the motherboard detects a 0°C reading, it assumes the thermistor wire has physically broken. If the printer kept sending electrical power to the heater cartridge without knowing the actual temperature, the aluminum block would melt. The system throws the MINTEMP error and kills the power instantly.
Step-by-Step Troubleshooting Guide
Follow these steps to safely diagnose your machine and clear the MINTEMP code.
Step 1: The Ambient Temperature Check
Before you take a single screw out of your printer, check your room temperature. Prusa printers have a built-in firmware limit: if the ambient temperature of the room drops below 15°C (59°F), the printer will throw a MINTEMP error upon boot. If you keep your printer in a cold garage or basement during the winter, use a hairdryer to gently warm up the hotend and the bed for 60 seconds. Then, press the reset button (the “X” beneath the LCD knob). If the printer boots normally, your hardware is fine—your room is just too cold.
Step 2: Diagnosing the Broken Wire
If your room is warm (above 15°C) but you are still getting the error, you have a broken wire. Look at your LCD screen. The temperature readings look like this: [Current Temp] / [Target Temp]. If the hotend reads 0 / 0, your hotend thermistor is broken. If the bed reads 0 / 0, your heated bed thermistor is broken.
The most common failure point for the hotend is right where the wires enter the aluminum heater block. For the heated bed, the failure usually happens at the back left corner where the wire bundle constantly flexes during Y-axis movements.
Step 3: The Multimeter Test
If you want to be 100% sure before ordering parts, test the wire. Open the Einsy RAMBo electronics case and unplug the suspect thermistor. Set a digital multimeter to the 200K Ohm setting and touch the probes to the thermistor plug pins. At room temperature, a healthy Prusa thermistor will read around 100K Ohms. If it reads 0 or infinity (OL), the wire has snapped internally.
The Permanent Fix (Hardware Replacement)
If your multimeter proves the wire is dead, or if the temperature jumps wildly when you wiggle the wire bundle, you cannot fix Prusa MINTEMP error without replacement parts.
You must buy a genuine E3D V6 thermistor (for the hotend) or a genuine Prusa bed thermistor. Do not buy cheap, generic thermistors off Amazon, as their resistance tables are different and will cause thermal runaway or terrible print quality.
You can grab the official, pre-crimped OEM replacement parts directly from trusted distributors like MatterHackers Prusa Parts.
How to Prevent This in the Future
Hardware replacements solve the immediate breakdown, but proper cable management extends the life of your machine.
When installing a new hotend thermistor, ensure the zip ties holding the wire bundle to the extruder carriage are snug, but not crushing the wires. For the heated bed, ensure the nylon filament support cable inside the textile sleeve is taking the stress of the Y-axis movement, not the actual electrical wires.
Finally, if you print in a cold garage, consider purchasing an official Prusa Enclosure or building a DIY Lack Enclosure. This keeps the ambient temperature stable, prevents warping on ABS/PETG prints, and permanently solves the cold-weather MINTEMP boot failures.
