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  • Protection against multiple power panics
  • Autonomous fan self-test
  • Incorrect firmware flashing protection
  • Min. temp safety trigger
  • Enforced fan check
  • Filament runout delay fix
  • Extruder position after fan error fix
  • Text format correction on Live adjust Z screen
  • Display target temperature at PID calibration screen

A detailed description of changes:

Protection against multiple power panics (for MK3S/MK3/MMU2S/MMU2)

In case of a rare scenario where the printer was in the process of recovering from the first power panic and a second occurred, it might have caused an error and fail the print. Starting this release, the printer is protected against multiple quickly-following power panic scenarios and it should always recover.

Autonomous fan self-test

In the previous release, the user had to assist during the fan test. Now, the self-test is fully automatic. Printer spins up each fan from low to the max RPM and measures the values. Since both fans on the extruder have a different range, it is possible to detect, whether they are connected to the correct socket on the board and whether the fan is able to reach its max RPM.

Incorrect firmware flashing protection

Each of our Original Prusa i3 printers requires a slightly different firmware. The system now checks whether you are flashing the correct hex file. For the future releases, if a wrong file is used, the user is warned during the reboot after the firmware is flashed. We are working on a feature in the PrusaSlicer, which will warn you before the entire process starts.

Min. temp safety trigger

In the case of min. temp scenario, the printer used to run the G-code on the background, but didn't execute any movements nor the filament loading, then displayed min. temp error. The new firmware will immediately restart the printer as soon as min. temp scenario occurs. This is a safety feature to prevent the printer from overheating as min. temp is mostly caused by damaged thermistor reading incorrect temperature values. After the restart, the user can start the print again, but please check whether the print starts correctly.

Enforced fan check

Previously during the "fan error" message, the user was allowed to continue printing without fixing the issue, this no longer possible. Until the error fixed by the user (e.g. removing the jammed filament from the fan), the print is paused. This is a safety feature preventing possible damage to the printer.


  • Filament runout delay fix
  • Extruder position after fan error fix
  • Text format correction on Live adjust Z screen
  • Display target temperature at PID calibration screen

Known issue for the future release:

Shifted print after a power panic

During our internal tests, it was discovered that after multiple power panics in a row, the printer sometimes slightly shifts the print up in the Z axis (tenths of millimeters) during the recovery. Although this is a very unlikely situation in real-world conditions, we are working on a fix.

Prusa Firmware beta testers group

Are you an experienced user, who wants to join our insider testing group? We are looking for skilled users, who are willing to help to improve the firmware. You will be given our most recent versions and provide feedback on any bugs or errors you might encounter. For the most active testers, we have prepared attractive rewards ;)

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