What is the problem?
Octoprint fails to start the part cooling fan while printing.
If the printer is Idle, it starts from Terminal (using M106 S255)
If I print from SDCard the fan works just fine.
The problem started two days ago. Before that, the part cooling fan worked like a charm.
What did you already try to solve it?
- rebooted Octoprint
- printed in Octoprint Safemode
- rebooted printer
- used different slicers / models / gcodes
- used terminal to send M106 S255 while printing
Logs (octoprint.log, serial.log or output on terminal tab, ...)
octoprint.log (53.2 KB)
Additional information about your setup (OctoPrint version, OctoPi version, printer, firmware, ...)
OctoPrint 1.3.11
OctoPi 0.16.0
Raspi 1 B+
Anycubic Chiron, V1.3.0
As you have discovered, the part cooling fan is controlled by the GCode commands M106 and M107. OctoPrint can control the fan when you are not printing, but once you start a print, the GCode commands will take precedence. There are plugins that can alter this behavior but it doesn't look like you have any installed.
Using a text editor, you can search the GCode file you are uploading for M106 and M107 commands. As a test, upload the following through OctoPrint and print it. You can also put it on the SD card and print it from there as well. Results should be identical.
fanspeedtest.gcode (187 Bytes)
Hey there
thanks for your replay b-morgan and thanks for that speedtest.
It did the same errors as before with that script but since I tested all day I found out it sometimes also occurs while printing from SD-Card, so it seems like a non-octoprint problem.
But thanks for helping!
-Marco
Have you checked for loose fan wire(s)?
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Yes, I checked for continuity from the FAN0 Connector on the board to the fanpins of the mainconnector at the hotend aswell as the connectorboard in the Hotend.
Connectionwise everything is fine.
After contacting anycubic support, they told me it's possibly a bad mainboard, hope they'll send a new one 
Thanks for your help!
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Good afternoon marco3993
Did you ever resolve this issue? I have recently purchased the Chiron and am having exactly the same issue. I can't figure out why as the fan GCODE is present but it just seems to ignore it.
Strangely i also can't print from the SD card as it randomly stops.
I've got a case open with Anycubic but wasn't sure if you managed to fix this.
Thanks.
Do you have some example gcode from your manufacturer? Just to rule out any other errors. If you got a example gcode try to print it via sd card. If it still not works I would contact the manufacturer.
@marco3993 Did you ever get this resolved with a new board?
Did you find a solution? My fan won't start either. Only when printing via SD card
Hello @Eaglefire, hello @awestley!
Yes, the TO found a solution marked in post 4.
It's always better to open a new thread the linking in to old ones.
If you open a new thread, please answer all the requests as good as possible.
Blue words (like logs, you see them on the right of the edit frame) are links.
Serial logging usually must be enabled before.
I still firmly believe that the problem is with Octoprint. It goes well with Pronterface or Repetier
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Then please open a new thread!
And give the information to get it fixed (if it is OctoPrint).
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@Ewald_Ikemann I was simply looking for confirmation the new board resolved it. I didn't think that opening a new thread to ask @marco3993 seemed like a good idea. 
If it fixed his issue, great. If not I would open a new thread. I do that because if I just opened a new thread everyone would say "This is already solved" and point me to this thread.
2 Likes
I have also encountered this problem. Have you resolved it and how to solve it
Hi there,
It was a blown Transistor as far as i remember, anycubic sent out a new board, which fixed the Problem.
If memory serves me well, i reflashed marlin on my Chiron to use the other fanport on the board while waiting for the replacement