I have checked the fan wires and everything is plugged and seated correctly.
It might be a bad fan wiring or sensor. Should I just replace the hot end assembly, and maybe the extruder connection board? A user on reddit had to replaced their front housing assembling to fix this.
Also is it common for support to to ignore a trouble ticket for a over a week? Are failed or defective components covered by the warranty?
Thanks in advanced!
I had the same problem on a weeks-old P1P. They sent me a new nozzle fan after a couple weeks. I did not expect it to fix the issue, but it did. Not sure how a fan can fail after only a dozen hours or so of use, but that seems to have been what happened.
I’m hoping Bambu Lab support reaches out to me also. I went ahead and ordered a replacement hot end assembly, since it has the fan, heater & thermistor already installed
I replaced to hot end assembly which resolved the issue, but I still want to fix the original hot end assembly to keep as a spare.
Bambu Lab support reached out to me, but they want video evidence of the fan problem before they’ll process their warranty.
@sntran0 Hi, do you mean something like this?
Since all fans are closed loop, the hotend wires which you might have not fixed using the little hook beneath the connectors cause those issues by simply touching the fan and thus lowering its speed. Ergo, the actual speed deviates from what is supposed to be like.
Hello guys, I had a clog in my stainless steel nozzle, a changed the nozzle, but i kept sending error, of nozzle temp. When i changed the complete hotend, to a hardened steel, now says fan speed abnormal, despite i changed the settings. Any further ideas what it can be?
I had the same error a couple of weeks ago and my fan which was only two weeks old had gone bad. I put a new fan on, and it fixed the problem.
I have just had this issue when changing over the hotend. I resolved it by re-seating the hotend fan connector whilst the printing was powered on. The fan turned on at this point, then turning the printer off and back on again.
It’s now printing fine with no issues.
I had the same error once when swapping hotends. I undid the wires and reseated them which fixed my issue.
Had the same issue and after assembling/disassembling twice I realized I had put the fan on backwards. Confirm that the fan is facing the same direction it was when uninstalled or check the Bambu Labs docs/videos to compare.
The correct placement for me had the QR code facing out and the fan label flush against the nozzle.
Encountered this same hotend fan speed abnormal error after installing a brand new .4 hotend for the first time. Reseated the connectors many times while the printer was off to no avail - but repeating these steps while the printer was on, I noticed the fan kicked on immediately. These steps worked perfectly, thanks for the help Roley.
I also reseated the hotend fan WHILE the printer was ON. The fan started immediately.
I have had a similar issue when swapping out the .4mm hotend with either a .6mm or a .2mm one. At one stage I kept getting “The hotend fan speed is abnormal” error every time I started the printer going again, even when re-fitting the .4mm original hotend that was working fine before I swapped it out. I was begining to get a tad frustrated (“tad” being a reference to the Airplane movie, yes I’m that old). I had almost given up when I came across the Bambu Wiki where it mentions checking thet the hotend plug has been fitted and seated correctly. It appears that, for the P1S, it’s quite easy to not quite fit the plug correctly, not helped by the crramped and tight working space. Using a bright light source and carefully checking the plug was lined up correctly and also seeing that the other two connectors also lined up with the hotend one I was able to get the .4mm hotend to work again. Then I tried the .2mm one again (all with power off inbetween, because it looks like its quite easy to short the connector) and to my relief I managed to get the .2 hotend working.
It would make life a lot easier if the connectors were easier to unplug and refit without it having to be so difficult to align correctly.
Just thought I’d share my experience and relief after I had just called the machine all the names I could think of!
Roleys tip worked perfectly , thanks ,tried half a dozen times and still got the error , then reset the connector with it over 50 degrees and printer still on and the fan started.
Man I wish this worked. Still no luck on my end.
Thanks for the info. I do not think I would have had it switched on, but it works. I had to do it a few times, thanks again
Thank you, just ran into this problem myself and reseating the connector didn’t help. Thanks to your comment I unplugged the printer and then replugged it in and restarted the print and now it’s fine again 
So thanks! Was worried I’d end up needing a new nozzle after only a couple months of use
Same problem as everyone else, reconnecting the hot end fan while machine was on fixed it. Its odd that despite Bambu advising not to connect any type of electrical connection while the machine is on that this method actually works. Seems like a firmware upgrade is calling. Hopefully Bambu Labs are taking note and will fix this ridiculous issue.