Prusa error 13825 (MCU in Buddy Overheated) appears on the MK4 and its equivalents are #31825 on the CORE One, #35825 on the CORE One L, #26825 on the MK4S, #27825 on the MK3.9S, #28825 on the MK3.5S, #21825 on the MK3.9, #23825 on the MK3.5, #17825 on the XL, and #12825 on the MINI. The temperature sensor on the Buddy board detected that the MCU has exceeded its safe operating temperature, and the printer halted to prevent hardware damage.

What the Error Means

The Buddy board MCU generates heat during normal operation, which is dissipated through the board’s ground planes, the enclosure, and the surrounding air. If the electronics bay does not have adequate airflow — most commonly because the printer is sitting inside a DIY enclosure that encloses both the print chamber and the electronics — the MCU temperature can rise until it hits the thermal cutoff. High ambient room temperature (above 30°C) can contribute even in open setups. Loose connections on high-current connectors (bed power, PSU) also cause localized heating near the xBuddy board that can affect MCU temperature readings.

Step-by-Step Fix

1. Remove the printer from any enclosure. If the printer is in a sealed cabinet, move it to an open location with free airflow. The electronics bay must breathe — even if the print chamber benefits from enclosure, the Buddy box must remain exposed to ambient air. Route the electronics outside any enclosure walls.
2. Allow the printer to cool before restarting. The MCU needs to drop back below its threshold before printing can resume safely. Give the printer 20–30 minutes in open air.
3. Check the ambient room temperature. If the room is above 30°C, improve room cooling or relocate the printer to a cooler area. The printer is rated for ambient temperatures up to approximately 30°C.
4. Clean dust from the electronics bay vents. Accumulated dust acts as insulation. Use compressed air to clear dust from the Buddy box’s ventilation slots and from the board surface.
5. Inspect high-current connections at the xBuddy board. Loose PSU, bed heater, or motor connections create resistive heating at the connector pins, which can raise the board temperature. Check that all major connectors are fully seated and show no discoloration.
6. Contact Prusa Support if the error recurs in normal conditions. If the printer is in the open at room temperature (under 25°C) and the error still fires, the board thermistor or power delivery may need evaluation.

Parts Required

• No replacement parts are typically required for this fix — basic tools only
• Compressed air canister (for dust removal)

If the error continues after improving ventilation and the printer is not enclosed, contact Prusa Support at help.prusa3d.com with details about the printer’s environment and temperature readings at the time of the error.

Frequently asked questions

What does Prusa 13825 mean?

Prusa error 13825 (MCU in Buddy Overheated) appears on the MK4 and its equivalents are #31825 on the CORE One, #35825 on the CORE One L, #26825 on the MK4S, #27825 on the MK3.9S, #28825 on the MK3.5S, #21825 on the MK3.9, #23825 on the MK3.5, #17825 on the XL, and #12825 on the MINI. The temperature sensor on the Buddy board detected that the MCU has exceeded its safe operating temperature, and the printer halted to prevent hardware damage.

How do I fix Prusa 13825?

Prusa error 13825 means the Buddy board MCU temperature is unsafe. Learn how to improve electronics ventilation and prevent overheating in enclosed printing setups.