# Specific 3D Printers, Scanners, & Hardware > FlashForge Forum >  Active cooling - Fan not turning on automatically when set to 100% after layer 2 :-(

## cdl0012

I've searched the forums but couldn't find the solution to probably a very easy problem.

I printed the active cooling duct from thingiverse, wired up a 40mm 24v fan to the "EXTRA" power that is labeled on the PCB of my Flashforge Creator Pro.

When I set the parameters in Simplify3D for cooling (ie. Layer 1 = 0%, Layer 2 = 100%), the fan does not automatically turn on at layer 2.

However, if I go into the menu options and "Set Cooling Fan" on, it turns on without any issues.  Thus the wiring is correct, I just can't get it to automatically turn on during the print.

What am I doing wrong?  It has to be something obvious that I'm missing.

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## Geoff

> I've searched the forums but couldn't find the solution to probably a very easy problem.
> 
> I printed the active cooling duct from thingiverse, wired up a 40mm 24v fan to the "EXTRA" power that is labeled on the PCB of my Flashforge Creator Pro.
> 
> When I set the parameters in Simplify3D for cooling (ie. Layer 1 = 0%, Layer 2 = 100%), the fan does not automatically turn on at layer 2.
> 
> However, if I go into the menu options and "Set Cooling Fan" on, it turns on without any issues.  Thus the wiring is correct, I just can't get it to automatically turn on during the print.
> 
> What am I doing wrong?  It has to be something obvious that I'm missing.


It's all down to the GCode you are using. It needs to send an M106 command to the printer when it needs to turn on, ie M106 S250 (where S=speed, 0-255)

Since I use makerware alot (and I mean ALOT) for my flashforge and ctc, there is no way to add the fan command unless you use Proftweak and even that has issues. I ended up doing the following to get around it.

I cut the main fan from the left extruder. From its two wires, I piggy backed 2 female connectors (I use XT60 as i use them alot of R/C stuff) 

I then copied this on the other extruder - so there is 4 female connectors above my hotends.. 2 for left and 2 for right.

I put a male connector on the cooling fan and on the left extruder and plugged them back in. So I am running 2 x 24v fans off the one output. So basically, the cooling fan runs whenever the extruder fan runs (and this doesn't seem to load the motherboard up much at all) Did the same for the Right extruder fan.

If I want to switch to the right extruder but have cooling for it, I simply unplug the cooling fan and plug it into the female for the rights fan and vice versa, that way no matter which side you print on, you can have active cooling - and only need one extra fan.

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## curious aardvark

Mine is currently wired into the same connector as the motherboard fan. 
basically comes on with power. 
I'm going to wire in a small switch so I can switch it off if necessary.

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## Geoff

> Mine is currently wired into the same connector as the motherboard fan. 
> basically comes on with power. 
> I'm going to wire in a small switch so I can switch it off if necessary.


Yeah a switch is the go I reckon, I just have to get around to installing it. A 3 way toggle switch, left is left extruder cooling , middle pole is off and right pole is right extruder cooling.

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## warkmal

Simplify 3D uses a modified version of GPX to generate the x3g from the gcode.  They may have a flavor mismatch.  They need to emit M126 if they're using the MakerBot gcode flavor parameter to GPX.  The typical slicer emits M106 to turn on the fan which will work for GPX in reprap flavor.  If they got this matched up wrong then it is commanding the extruder fan instead (on does nothing because it's on >50C anyway and off is bad and could cause a clog).

Also, the x3g protocol really only has a command for ON and OFF.  Any speed > 0 is translated to ON and speed = 0 is translated to OFF.

So, you could see what they're emitting by saving as gcode and looking for M106 or M126 in the gcode file.  Figuring out what flags they're sending gpx is harder, but we could figure it out from decompiling an x3g and comparing it to the gcode.  It may just be a bug in S3D.

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## Geoff

> Simplify 3D uses a modified version of GPX to generate the x3g from the gcode.  They may have a flavor mismatch.  They need to emit M126 if they're using the MakerBot gcode flavor parameter to GPX.  The typical slicer emits M106 to turn on the fan which will work for GPX in reprap flavor.  If they got this matched up wrong then it is commanding the extruder fan instead (on does nothing because it's on >50C anyway and off is bad and could cause a clog).
> 
> Also, the x3g protocol really only has a command for ON and OFF.  Any speed > 0 is translated to ON and speed = 0 is translated to OFF.
> 
> So, you could see what they're emitting by saving as gcode and looking for M106 or M126 in the gcode file.  Figuring out what flags they're sending gpx is harder, but we could figure it out from decompiling an x3g and comparing it to the gcode.  It may just be a bug in S3D.


Thats's good to know, thanks for that, it was one of the reasons I stopped using S3D

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## err404

Your mighty board may be missing the MOS-FET (PSMN7R0-30YL) for that connector. If so, you will need to solder one in to allow the fan control to work.
Edit: Sorry, I missed that it is working for you when you start it manually. For what it's worth, I use S3D with this mod and it works fine. I did not need to change any gcode, but I did have to tell it to start the fan on layer 2 in the process config.

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