Really helpful suggestion, you tried alcohol to get rid of the last few brain cells?
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I am too thick skulled!
On a related note.
I solved this by adding the Gcode M106 P2 S0 near the bottom of the machine start gcode.
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Is this still an issue in the current firmware? I have mine set to 0 and it’s always off when printing.
Ok so I dug into the Gcode further.
For your machine start Gcode:
Under the “set airduct mode”, replace with:
;==== set airduct mode ====
;==== if Chamber Cooling is necessary ====
{if (overall_chamber_temperature >= 40)}
M145 P1 ; set airduct mode to heating mode for heating
;M106 P2 S255 ; turn on filter fan
M106 P2 S{additional_cooling_fan_speed[current_extruder] * 2.55}
{else}
{if (min_vitrification_temperature <= 50)}
M145 P0 ; set airduct mode to cooling mode for cooling
M106 P2 S255 ; turn on auxiliary fan for cooling
M106 P3 S127 ; turn on chamber fan for cooling
M1002 gcode_claim_action : 29
M191 S0 ; wait for chamber temp
;M106 P2 S102 ; turn on chamber cooling fan
M106 P2 S{additional_cooling_fan_speed[current_extruder] * 2.55}
M106 P10 S0 ; turn off left aux fan
M142 P6 R30 S40 U0.3 V0.8 ; set PETG exhaust chamber autocooling
{else}
M145 P1 ; set airduct mode to heating mode for heating
M106 P2 S127 ; turn on 50% filter fan
M142 P6 R30 S40 U0.3 V0.8 ; set PLA/TPU exhaust chamber autocooling
{endif}
{endif}
;==== set airduct mode ====
Basically, the replacement M106 commands will set the fan speed to the variable you specify in the aux fan in the slicer.
For PLA, the layer change Gcode seems to have something that may re-activate the fan… I haven’t looked into that.
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Ok, so looking at the layer change Gcode, for filaments with softening temperature below 50 (e.g., PLA in the default settings), this line will activate:
M142 P1 R30 S40 U{max_additional_fan/100.0} V1.0 O45
I read from another post that R30 means the fan will activate when the chamber hits 30 degrees. U{max_additional_fan/100.0} basically means that the aux fan value you set the in slicer will represent the MINIMUM fan speed, which will activate at 30 degrees. If the chamber temperature increases further (to 40 degrees), the chamber fan will spin at full speed.
I have no idea what O45 means.
So I believe the solution should be to amend the line in the layer change gcode to as follows:
M142 P1 R30 S40 U0.0 V{max_additional_fan/100.0} O45
This will instead make the aux fan ramp up from 0% at 30 degrees to the aux fan setting you’ve set in the slicer, which it will achieve at 40 degrees.
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I just came here to add, same issue for me on the P2S. Once I start a print, I have to basically go to the touchscreen and watch it and every time it snapped the aux fan back on i toggled it off. This happens about 4ish times, then for the rest of the print (for me at least) it stays off.
i know i can modify the Gcode, unplug the aux fan, print a deflector, but this does not help me as a designer. Asking other people to print and install/modify something is an awful customer experience.
I design/print miniatures and this is so frustrating. X1C, same config, same file, same filament and conditions, flawless. Send it to the P2S and top interface layers go flying everywhere, supports warp etc.
@BambuLab - Please fix the Aux toggle on/off for the P2S (in the slicer) and make sure it stays off, there are some use cases where the Adaptive Airflow System actually does harm instead of help.
Slicer shows it’s off at 0% or 1% and still it turns back on to 40%, 50% etc as others have shown here.
As I mentioned above, the slicer setting by design only governs the minimum fan speed, and not the maximum. It’s easily fixable with a few modifications to the Gcode… of course a better option would be to allow both min and max values in the slicer.
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Absolutely and I could totally fix mine. im talking about all the other people who just print and dont modify gcode. this is a problem as a designer. you cant expect everyone to modify their gcode to print your model successfully for this 1 printer. This is a design flaw for sure.
I see. I get where you’re coming from then, since users can just downvote your model just because it doesn’t print right. It’s a totally different culture from other 3d printer brands.
I’m pretty nervous to just copy G-code into my P2S’s machine start G-code. I’d love a Bambu statement 
A reminder to anyone viewing this thread: the “Auxiliary part cooling fan” setting under Cooling in the Filament settings controls the LEFT fan.
If the setting doesn’t seem to be doing anything, it’s because you don’t have the Left fan installed. The printer is not “ignoring” the setting.
It does not control the Right fan.
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Any new information on whether this issue will be addressed in the foreseeable future?
It seems like everything is working at intended. I haven’t experienced any issues with the current setup.
The right fan being always on is part of the new “Adaptive Airflow System“ and takes the place of having to leave the door open like with older printers to ensure the chamber doesn’t get too hot for PLA.
If the right fan is impacting your prints, I recommend printing a deflector to point the airflow upwards.
Many posts in this thread seem to be from people setting the Left fan to 0% and then being surprised that the Right fan ignores that setting. Bambu Lab could address that issue by making sure to clearly label it “Left” fan in Bambu Studio.
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Seems not to be working anymore, at least not on the X2D.
I tried to set the M106 P2 to any value, but when chamber hits 30+ the aux fan gets to 70-80%
Same issue with the M142 P6, also not working.
I guess it’s now set in firmware…
According to my startup gcode, the aux fans are (X2D has 2):
M106 P2 S102 ; turn on auxiliary fan
M106 P10 S255 ; turn on filter fan
M106 P3 S102 ; turn on chamber fan
So it seems P2 and P10 are different on the X2D
Did you manage to solve this problem? It’s really frustrating that even after modifying the G-code and setting the auxiliary cooling fan to off in the filament settings, the fan still turns on. It makes no sense.
I just got my X2D. You need to modify the M142 settings as well. Change U (minimum fan speed) and V (maximum fan speed) settings.
Make sure you also change the layer change gcode, otherwise it will reset itself every layer change.
It’s not working for me (X2D)
But i found that the AUX fan is being overridden by the setting in Filament / Softening temperature.
For PLA this is set at 45, but if you increase, to like 70, the aux fans will only spin up to keep the chamber lower than this temperature.
Be careful, i had a big heatcreep clog…..
I have a P1S, and recently got a P2S.
I’ve had so many issues with the fan on the right side causing failed prints when I’m using Sunlu PLA+
I printed a bunch of Bambu Matte PLA without issue, so it seems like they can make things print fine in there without mods, but certainly don’t make it easy.
On the P1S I was having heat creep issues a lot, constantly having my nozzle get clogged up. I printed a riser where I can slide the glass lid back a bit, and since having that on my P1S I’ve had zero heat creep issues, have been printing for months with it now.
So, I printed a P2S version of the riser, and adjusted the filament profile to have the AUX fan at zero % and stopped having issues where the right side of models would have broken layers and lifting. Now they print fine.
I’m trying to dial in ironing however, and still notice the right side is less smooth than the left, so the damn fan is still an issue. So, I’m now printing ZombieGoat’s deflector, and am hoping that with that, plus the top glass slid back a bit, I should actually get the P2S to P1S quality with PLA 
It’s not great that I’ve upgraded machine and am having worse prints from it.
But if these two things help, then I would recommend this riser (I can’t include links): X2D / P2S Riser - AMS Flipper V2
And possibly the deflector if that helps as well as others are saying.