Not sure what is happening here but I noticed yesterday the chamber fan was spinning up and down a lot…
Printing PLA on textured PEI, never had this happen before. Is it a firmware thing or an issue with my printer?
That’s cool, but should it be fluctuating like that? or did recent firmware/studio updates cause it?
The V1.9.1 “fixed” a previous raised…
But the “fix” caused the noise everyone including you noticed and mostly hates, so I suspect they tweaked the code logic again and released another patch to adjust it \ balance it… (OR - they got the initial fix wrong and re-fixed it).
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Hmm the update just came through, I will do a test print later to see if it’s fixed the issue. In meantime I will double check the hotend cables are all good because I swapped back to my 0.4mm yesterday
I have two X1C, both updated. One runs completely erratic, one runs normal.
I have MacOS version 1.9.1.67
after last update for all types of plastic chamber fan starts from 100% and stay at 100% all time…tried to change G-Code at plastic advanced settings but nothing changes…
bambustudio 1.9.1.67 for MacOS 
Just want to add my chamber fan is still playing up when using the textured pei. fluctuating between 40/50/60 then boosting up to 100 and back down again. All the latest firmware and software being used.
Sorry to go on, but it’s been nearly a month and this is still happening. It’s a good job I primarily use PLA and not more heat sensitive materials where a stable chamber is vital.
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I’m also experiencing this exact issue. I was concerned my chamber fan might be failing at first, but I’m thinking after reading this is likely software-related.
Running most up-to-date X1C firmware and Bambu Studio.
Yes it is definitely a them problem, since I posted this I’ve seen a lot of people have issues printing with PETG too which is a filament that needs a stable chamber to get a good print. I don’t know if this fluctuating chamber fan is causing issues with it but it certainly won’t be helping.
My printer is in the same room I design in too, so having the fan start going mad at 100% then back down again constantly is very very annoying.
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I have an x1c with 7600hrs which is doing the chamber fan surging thing. I have just bought a brand new one and placed it next to the old one. Both have exactly the same settings, same firmware and printing the same part. The new one has the chamber fan steady at 50% occasionally going to 40% or 60%. The old one has the chamber fan at 80% fluctuating between 60%and then suddenly boosts to 100%.
I am suspecting a sensor issue??
I am going to submit a ticket tomorrow but wondered if anyone has figured this out?
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Yeah I have heard from people who have two machines, one has the issue, the other doesn’t. I’m assuming the fact the fan is still working that the issue has been caused by some other component used in certain machines that has been affected by the last firmware update.
Mad that it has been nearly 3 months and they still haven’t fixed it. I think that was actually the last update for the machine in general, we have only seen minor Studio updates and an AMS update since. Either they are happy the machine is now stable or they are focussing their energy on something else. Maybe a new printer, or fixing the A1, or just the Makerworld stuff…
Support ticket submitted. Managed to get an excellent video of the chamber fan flitting between 20% and 80%. I will update if it gets fixed and what the faulty item is.
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Based on some early testing this morning I think the firmware update that dropped today has fixed the issue 
EDIT: No, it hasn’t fixed it, 45 mins into the print and it’s started ramping up to 100% again
Opened a ticket, after some tests they said it needed a replacement chamber fan. Ordered one and fitted it today and it has cured the problem. Upon looking at the old fan (done 7600hrs) apart from it being dirty it was very loose on the bearing. My guess is the sensor was telling it to spin up but was having resistance and then suddenly overcame the resistance and surged. Anyway problem completely cured and I am happy. You can’t fault Bambu support. Everytime I have had an issue they have resolved it quickly.
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Hey nice one mate, I will order one myself and see if this fixes the issue!
So I installed the new chamber fan and so far so good in terms of it ramping up. I do find it odd that many people had this issue at the same time, so my theory is still that the firmware update broke the sensor in the old model fans and only the newer ones work…
Here are a few pics of the installation. I would like to add the supports on the right-hand-side snapped off when I unscrewed the old fan. These look VERY brittle and have very little plastic supporting them. I’m not sure if they have improved this design in newer printers but something to look out for.
EDIT: So while it was ironing my print the fan was boosting up to 80% so I really don’t know if it did fix it.
Old vs New
Oh dear
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Well two weeks later…the fan is still surging instead of an incremental ramping up of speed. it goes from 20% to 80% in an instant and then back down. So it doesn’t look like the new fan fixed the issue. The weather is getting cooler here now so the issue is not as evident. I cant spend anymore time on trying to figure this out especially as its not doing it when we have hot weather. I am guessing its a problem with either the wiring or the temp sensor.