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Print fan is not spinning

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MK2.5
MK2.5S
MK3
MK3S
MINI
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The print fan is the fan blowing on the printed object, right below the nozzle. Depending on the material and where you are in the print it might not always spin at full speed or at all. There is also an error in the firmware connected to the fan not spinning. If you did not receive any error but the fan does not spin, you will probably find the solution in this article.

MK2/S, MK2.5/S, MK3/S/+ print fan (green circle)MINI/MINI+ print fan (blue arrows)
You can easily test the print fan function from the LCD menu -> Settings -> Temperature -> Fan speed. Always test with at least 50% power (value 127-255). When you select the speed, confirm by pressing the knob.

PrusaSlicer settings

The print fan is never used during the first layer of any material. It will start from layers 2-4, depending on the material profile selected. For example with PLA, the print fan is spinning at 100% all the time until the print finishes. For ASA and ABS, the fan is turned off completely for the first 4 layers then will only spin at 15-20%, with a slight increase when printing Bridges. At very low speeds the print fan can be almost inaudible.

 
PLA settings - Fan always 100%ASA settings - Fan only 20% at fewer layers.
To see the cooling options in PrusaSlicer you must have it set to Expert mode.

Further checks

Make sure that the fan is:

  • Plugged into the right location
  • Plugged in in the correct orientation
  • Plugged in completely and making good electric contact

If the fan still doesn't spin up, you can unplug it from the electronics board and test it with the 12V DC (MK2/S) or 5V DC (MK3/S/+) power source. If the fan spins up with an external power source, check the electronics for your printer and its fuses:

 

5 comments

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Tom in MN
•
On a MINI+, I had a print pause with the "print fan not running" message after just a few layers (around the time the fan would be starting after being off for the first 3 layers). It passed the diagnostics. I raised the min print fan speed in the Prusa Slicer Filament settings to 35.  It was at 30, but the default is now 35.  That seemed to have fixed the problem
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Motylum
•
For people whose printer worked for a long time without any problems and then starts having print fan errors sporadically, try testing the print fan from the printer menu while pushing on the printhead's cable harness to one side or the other (try near the printhead itself). If the fan spins up while you do that, you have your culprit. The print fan cables are quite delicate and can wear out over time as the cable harness bends cyclically. If one of the voltage supply cables is broken, the fan will not work. If the signal cable is broken, the fan can work, but will not react to the printer's signals, resulting in an error too. In any case, bypassing the wires (all three to be sure) is the only real option.
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Gauthier W
•
Bonjour
Depuis quelques heures, le ventilateur d'impression ne tourne plus durant l'impression, il tourne lorsque je l'active dans les réglages mais il semble avoir des difficultés et on peut entendre une variation d'intensité régulière. (Petit pique d'intensité tout les 5 sec environ)
Je pensais que c'était à cause de la poussière alors je l'ai dépoussiéré et constatant que ce n'était pas ça, je l'ai débranché puis rebranché.
Le problème persiste malgré tout et je n'ose pas imprimer sans ce ventilateur.
Que faire?
 
Cordialement 
Reply
LeoHstr
•
J'ai le même soucis :(
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William H. - Official Prusa
•

This would depend on what filament you are printing with. Like, with ASA and PETG there will be a varied and much less speed on the fan. You can follow the steps in the article below for how to troubleshoot it:)
https://help.prusa3d.com/en/article/err-print-fan-error_2159

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William H. - Official Prusa
•

This would depend on what filament you are printing with. Like, with ASA and PETG there will be a varied and much less speed on the fan. You can follow the steps in the article below for how to troubleshoot it:)
https://help.prusa3d.com/en/article/err-print-fan-error_2159

Reply
Cameron library
•
Hi! Are there instructions on how to " ...and test it with the 12V DC (MK2/S)....power source. "
Thanks
Chris
Reply
Giuliano - Official Prusa CS
•
Hello. There are no instructions because it's a simple operation: just connect the fan with a power source which can be 12 or 5 V according to the printer model.
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Robert Schiele
•
After completely assembling the printer, the self-test reported that the printer fan is not working and suggested a wiring problem. I checked again all the connections without any findings. Finally, I measured the connectivity from one end of the cable to the fan soldering points and found that while the red and yellow wires were conductive, the black wire had no connection at all. Therefore I wondered whether I might have squeezed the cable while assembling even though taking care not to do so and disassembled the relevant parts again. The result is that the cable does not show any sign of stress over the full length.
At the moment the only option that comes to my mind is soldering a replacement black wire to the fan but I am open to better ideas.
The test protocol that was included with the assembly kit states that the print fan was tested ok. Does that mean you tested the physical operation of exactly the fan that was included in the package or did you just test the board whether it could operate a fan properly?
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Giuliano - Official Prusa CS
•
Hello. The components are tested indivisually for the kits. You can contact the technical support via email or live chat to report this problem, so they can evaluate if it's a defective component or if something went wrong during assembly.
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