Successful repair operation to replace the extruder fan on the Prusa i3MK3 3d printer. As previously reported, I was receiving sporadic temperature failures, which eventually lead to complete failures whenever the first layer was completed. The screen indicated either a TMC overtemp error, or a Crash Detected.
In reality, it was neither. Instead, it was a broken connection on the front extruder fan, resulting in either a loss of connectivity or a short circuit. I would have easily wasted a lot of time troubleshooting issues but ended up stumbling onto the fix accidentally. During my testing, I flashed the firmware, and then opted for a full reset of the calibration. This was in the theory that something was causing an actual crash, potentially with the print bed. However, the first stage of that testing validated the fan connections, resulting in a failure on the front fan.
From there, the fix was simple – replace the fan. That of course was more problematic with the cable routing of the machine, but the parts in general were rather inexpensive. I ended up opting for an Amazon supplied kit, 2 fans for about $16, both of which can solve the problem. After a bit of a learning curve, I had the cables re-routed and the new fan installed and was able to run thru the recalibration steps successfully. A short print validated that the errors were now gone – no crashes or overtemp errors.
The sporadic temperature overrun errors I am not sure about – I can’t reliably recreate the error, so only time will tell me if that is fixed as well (may have been the loose cable, or some other cause). I will report if the issue comes back or seems to be gone long term.
My only issue at this point, other than a lack of PLA currently, is the build quality of the fans themselves. They work, the wiring is solid, and they are the exact size. However, the one I ended up installing seems to have a poor assembly tolerance since the fan itself rattles a bit depending on the extruder movement. Not a showstopper but sounds like the fan blades striking the casing. When I have time, I may re-swap for the second fan, and see if it still has the same issue. Otherwise, the fan itself is much quieter than the stock one, so it would be a nice improvement.
If you need a replacement fan, try the following link for the option I used:
