MK4 - filament sensor - inconsistent - possible fix
Since new - I have had issues with the filament sensor on the MK4 - false reporting "no filament" - I contacted support - recommendation was to open the filament door and blow out the drive gear area - no change. Found that as I rotated the filament - ie, from 270 deg to 180 deg, or from left to facing forward - the sensor would indicate "no filament" - in desperation - I removed the 3 screws that hold the planetary gears in place on the front of the extruder - removed the planetary gear set - reinstalled the drive gear/planetary gear set - that must have dislodged material I couldn't see - because the filament sensor is now working correctly - ie, the filament can be inserted and rotated 360 deg - remains detected! As an FYI - this is a factory assembled printer - and I am not recommending anyone disassemble their printer - but this worked for me....your mileage may vary....
RE: MK4 - filament sensor - inconsistent - possible fix
I'm having the same issue. I can basically wiggle the filament about 2 inches above where it inserts and the printer will throw a fit about filament being there/not being there. Engaging Prusa support now and expect to hear more about blowing out the drive gear area from them.
RE: MK4 - filament sensor - inconsistent - possible fix
I don't want to claim victory too soon but it seems that some PTFE grease spray in the hole above the gears has solved the problem. at least temporarily
RE: MK4 - filament sensor - inconsistent - possible fix
Please go into the menu and put the Filament Sensor readings in the footer. Then you can investigate the problem more accurately and check if the steel ball is stuck or if the readings are completely rubbish and the sensor is broken.