P1S after updated to 01.09, the printer report HMS_0300-0400-0002-0001: The Part Cooling Fan speed is too slow or stopped error.
After downgrade to previous version , all fixed.
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Had same error code… i bought another fan because all wires were good… if this is a firmware bug i would like to know !
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I updated this morning to P1S firmware 01.09.00 and just experienced a comically frustrating series of failed print after failed print. Previously had none of these issues. The only thing that changed was the firmware update. Just downgraded back to the previous 01.08.02 and now it’s back in business.
Definitely something is incorrect/wrong with 01.09.00
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Same here…reverting to previous version worked…almost ordered a new fan…What the f**K???..fix please…
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Same here. Updated the firmware and now getting this error out of nowhere. I checked the connector and cant see any issues. the fan will spin freely if i try to spin it with my finger. Looks like in the slicer settings that fan is turned off completely - but I didn’t do this manually. This only started happening after the firmware update. Will likely roll back.
Newest version of studio is also screwing up AMS mapping, it thinks i have nine AMS slots when i only have one AMS so im not sure whats with these updates.
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same for me
I would also like to know if and when a version will be released that solves the problem.
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I guess nobody at the Bambu end reads these, since there has not been a new update released yet…sad.
AMS mapping might be model related. I routinely have issues with Makerworld models carrying the model uploaders configuration with it. To the point where I expect to have to select Overwrite to resync the AMS devices, the types of filament, and the color of each spool.
I’ve always assumed that it is a setting that uploaders should turn off, but don’t when they upload a model to Makerworld. Not uploading models myself, that is just a guess on my part.
Hi, I have same issue with part fan not going. Handy app showed error, computer showed nothing just turns fan off. I have downgraded to release by release but not solve problem. currently trying 01.07.00.00 but still same issue. Any ideas??
Finally upgraded one of my P1S printers to firmware 01.09 and first thing that gets printed (Flow Rate calibration) the HMS 0300-3100 error gets thrown. 
Looks like Ill be downgrading to a previous firmware version.
Surely to goodness they would not drag fixing this issue to sell more P2S units?..surely not… 
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Upping that topic for visibility… same firmware / printer and I get that error too.
Weirdly enough if you activate the fan through the screen the fan WILL turn on BUT the UI on the screen still say it’s off.
While the chamber fan it will show as “OFF” then when you click to activate it the UI turns to “ON” (and so does the fan).
I am guessing there is something here to be looked into, seems the printer doesn’t seem to get proper feedback from the fan and believes it’s off when it is running (well should be running because during printing it doesn’t seem to be running).
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Adding further info : I downgraded the firmware through the mobile app, and I don’t get the error now.
PS : having the downgrade option in the PC client would be great 
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so i recently updated and this is the error I still get HMS_0300-0400-0002-0001: The Part Cooling Fan speed is too slow or stopped. It may be stuck, or the connector may not be plugged in properly.. weird part is the fan is working fine and still printing fine.
How did you downgrade? I am new to having a Bambu Lab P1S and I am having the same issue.
Welcome to the forum.
You can use the Handy app to downgrade the firmware.
It would be as the latest upgrade is laggy big time
I am also facing the similar issue on part cooling fan..and its too annoying
HMS_0300-0400-0002-0001: The Part Cooling Fan speed is too slow or stopped. It may be stuck, or the connector may not be plugged in properly. but it going and printing but
there also this sound like screw loose or something
I mean my is saying th error code and has not stop but also is making a sound