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Are the fans running?  

Active Member
Are the fans running?

How to know if the fans on the print-head on the Prusa original Mk3 are running?

After finishing a long print (11 hours) I noticed a smell of ‘burnt caramel’ in the room where I print, which I had never noticed before when using PLA filament. After cooling and startup the smell was there at once, again.

I could tell the fan on the side was running as it drew smoke in and could be heard hitting a small piece of filament I pushed in. (I took it our again at once of course). The second fan - the one blowing near the nozzle I am not so sure about.

I cannot see the blades moving (but am not sure I should be able to see them) nor does it pull smoke in, nor can I get the ‘blades hitting a small piece of filament’ sound.

So, to questions:

1) would the printer ever operate if one fan was not turning?

2) is the printer likely damaged now, if it ran for hours with one fan not working?

Best wishes, Peter.



Posted : 28/03/2021 6:09 am
RE: Are the fans running?

On the Mk3, there is an option for fan speed monitoring, if it's turned off, the printer will run without alarms with the part fan faulty...
If you look at some of the chinede printers they have no part fan at all... Geetech Prusa i3 ProB for instance. 
you can print some filaments without  a fan..   for instance, I printed a new fan shroud in PETG.  without  fan...   which is just as well, because the orignal  fan shroud was distorted and dysfunctional...  (I don't print ABS or ASA)


regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 28/03/2021 1:05 pm
Dan Rogers
Noble Member
RE: Are the fans running?

Touch the center of the fan - not the blades - if it is spinning you will be able to tell with your finger

Posted : 29/03/2021 6:48 pm