MK3S/MK3.5S Print Blower Fan Adapter (MK4S Fan on MK3.5S + Revo Six)

I recently upgraded my MK3S to an MK3.5S — a solid upgrade overall. However, I felt the part cooling was lacking, so I decided to experiment by using the MK4S print blower fan on the MK3.5.

This mod adapts the MK4S blower fan to fit the MK3.5, using a mix of modified original parts from both the MK3S and MK4. 

It’s designed around the Revo Six hotend, which I’m currently using. Fitment with the stock MK3.5 hotend hasn’t been tested, so your mileage may vary.

Since this mod adds extra weight to the print head, I highly recommend recalibrating the input shaper using the official Prusa accelerometer set. I'm still testing this setup, and I plan to add space or an adapter to make it easier to mount the accelerometer directly.

⚠ Important Notes:

I haven’t confirmed whether the MK4S fan draws more current than the MK3.5 board can safely supply — use at your own risk.

Works with a Revo Six hotend; stock hotend compatibility untested.

Minor tweaking may be needed depending on your specific configuration.