New Aux Fan Not Working

Bambu Lab P1 Series User Mods
1

Hi all.

I recently tried to add a second auxiliary fan to my P1S to get cooling on both sides for some silk PLA (specifically, Bambu Lab PLA Silk+ 13603). The side of a one of my prints that does not face the aux fan has some overhang issues, so I tried other things (drying the filament, slowing down printing speed, calibrating filament settings) besides adding the fan to avoid having to make any mods. I wasn’t able to solve it so I went on to mod my printer.

I didn’t find anything super useful except the following post:
Bambu P1S Aux fan cable splitter - Bambu Lab P1 Series / User Mods - Bambu Lab Community Forum

I ended up buying the Noctua FH2 and some other 12V PWM fan to connect to the aux port. I ended up cutting the connector off the stock aux fan, soldering that connector to a 1x4-pin Dupont connector via 28 AWG wires, connecting that to the input port of the FH2, soldering 28 AWG to the cut aux fan wires & adding a 1x4-pin Dupont connector, connecting the stock fan to port 1 of the FH2, and lastly connecting the additional fan to port 2 on the FH2.

bambu fan aux fh2 split
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Once I powered the printer on, I heard a small pop, but didn’t see any smoke. Unfortunately, the fans did not power on. I then tried to reconnect the original fan back to the motherboard by itself, but that didn’t work either. I then tried the other fan by itself and there was a pop that came from the fan (I did it for science and out of my own stupidity/curiosity). I checked to see if there was any resistance in the wiring, but there wasn’t any. I also tried using the power supply that Noctua makes for the FH2, but that didn’t work either.

From here, I decided to order a new aux fan. Once I got it, I installed it on the printer, but even that one didn’t work. I suspect I damaged the motherboard, but I’m not sure where and I’m super hesitant to just take out the motherboard at this point (because more work :sob: ).

Does anyone have any clue of what I may have damaged? Also, does anyone know how I should go about adding a second aux fan? I know I could also just connect the second fan in place of the chamber fan, but I’d rather just run both aux fans off the fan_2 port. If there’s no other way, then I guess I’ll just have to relent and find a nice way to hot swap the fans without having to remove the back cover.

2

Given what you’ve described, it sounds like you’re going to have to replace your board.

Not sure what you did, but it’s possible you wired your connectors wrong. You may want to double check your pinout since the Bambu Aux fan wire colors aren’t exactly intuitive. Something else to consider is that the Bambu Aux fan is a 12 watt fan and adding a secondary fan may have been drawing more current than the port could support. If you look at most configurations, they are using both fan ports on the board or are using one port, but supplying power to the second fan directly from the power supply

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I think you misunderstood how to wire things up. (Not trying to offend) You shouldn’t use a fan hub like the FH-2 because that could cause current overload. I’m afraid you might have wasted your money on the hub. :pensive:

If you read the title post, and read the desc of the model, then you should know that for the second aux fan, only connect the PWM and tach* and connect the 12V terminals to V+ and V- on the power supply.

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Hope this helps!

*The tach signals could interfere with each other. If you get a fan speed error or the fan speed readout looks abnormal it’s a good idea to disconnect the second tach.

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Not necessarily true. The FH2 has the ability to plug in an external power source which would have prevented the excessive power draw. It’s perfectly fine tor the scenario, just that it would have been best to use an external power source since the available output is not known on the board plug.

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Ah, I see. Yeah, I completely misunderstood how to wire things up :man_facepalming:. I’ve ordered a new MC board. Hopefully, I don’t screw this one up. If it ends up working, my plan is to make a video documenting the process so others can do it, too, if they want to. Thank you for your help and that diagram!