Prusa error 13213 (MCU Maxtemp Error) appears on the MK4 and its equivalents are #31213 on the CORE One, #35213 on the CORE One L, #26213 on the MK4S, #27213 on the MK3.9S, #21213 on the MK3.9, #17213 on the XL, and #12213 on the MINI. The Buddy board’s internal temperature sensor detected that the MCU has exceeded its safe operating temperature, causing the printer to halt.

What the Error Means

The Buddy board contains an onboard temperature sensor that monitors the MCU die temperature. If the MCU runs too hot, firmware stability is compromised and the printer stops as a precaution. The most common trigger is operating the printer inside an enclosed cabinet or DIY enclosure that traps heat around the electronics — the electronics bay must remain open to ambient air even when the print chamber itself is enclosed. Dust accumulation blocking internal airflow, a faulty board cooling fan, or a genuine board thermistor malfunction are secondary causes.

Step-by-Step Fix

1. Remove the printer from any enclosure. If the printer is inside a cabinet or custom enclosure, move it to an open location with free airflow around all sides. Electronics cannot be enclosed even when print chamber enclosure is desired — route electronics outside the enclosure if needed.
2. Let the printer cool to room temperature. Allow at least 20 minutes before restarting.
3. Clear dust from the electronics bay. Use compressed air to blow dust out of the Buddy box vents and off the board. Dust acts as an insulating layer and prevents heat dissipation.
4. Verify the internal board cooling fan operates. With the printer on, confirm that any cooling fan inside the electronics bay is spinning. Replace it if it is not.
5. Check ambient room temperature. The printer is rated for ambient temperatures up to approximately 30°C. Operating above this in a warm room or near a heat source can push the MCU over the threshold even with good ventilation.
6. Contact Prusa Support if the error occurs in normal conditions. If the printer is in an open location at normal room temperature and the error still fires, the board thermistor itself may be faulty and require board-level repair or replacement.

Parts Required

• No replacement parts are typically required for this fix — basic tools only
• Replacement Buddy board (if thermistor is confirmed faulty — contact Prusa Support first)
• Compressed air canister (for dust removal)

If moving the printer to a well-ventilated location does not resolve the error, contact Prusa Support at help.prusa3d.com with details about the printer’s operating environment.

Frequently asked questions

What does Prusa 13213 mean?

Prusa error 13213 (MCU Maxtemp Error) appears on the MK4 and its equivalents are #31213 on the CORE One, #35213 on the CORE One L, #26213 on the MK4S, #27213 on the MK3.9S, #21213 on the MK3.9, #17213 on the XL, and #12213 on the MINI. The Buddy board's internal temperature sensor detected that the MCU has exceeded its safe operating temperature, causing the printer to halt.

How do I fix Prusa 13213?

Prusa error 13213 means the on-board MCU temperature sensor reported an overtemperature condition. Learn how to improve airflow and diagnose board thermistor issues.