Question CPU fan error 90B - No min fan speed

Dec 30, 2020
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I have a cheap Win10 HP desktop PC 570-p033w that suddenly started having cpu fan issues. It's basically stopping completely under idle and then roaring back to max speed after a second or two, slowing back to normal, stopping again, and repeating this cycle over and over. If the cpu is under greater load, such as watching a video or playing a game, it will usually NOT do this and keep spinning quietly at a moderate speed. Internal temps are remaining normal (10c - 30c) all the time so there are no overheating issues causing this. I will also sometimes get a 90B fan error on reboot, but not always.

I replaced the 4-pin cpu fan with an identical new one - no change. I removed the heatsink, cleaned out what little dust was there and reinstalled with fresh thermal paste - no change. I installed a couple of different monitoring progs, SpeedFan, HWInfo, etc and found that there is no minimum fan speed set for the cpu fan. I dont know if one was present before but I suspect it was and dont know what changed it. It seems to me if there was a minimum speed value, the fan would not be repeatedly stopping at idle. I updated the BIOS and attempted to set the min speed there under the Thermal tab, but it gave me no option to do so (even though HP support indicates I should be able to). It just displays the current fan speed. I'm also not able to control the fan speed through the software I mentioned above.

Could a Win10 update cause this? Is there anywhere else this can be changed in OS settings? I have checked power settings and can't find anything there. This is getting extremely annoying.
 

Paperdoc

Glorious
Ambassador
Lots of current mobos have an option on the CPU_FAN header (and others) to set up your own "fan curve" - that is, the graph of what speed the fan should run versus what temperature is measured - rather than the default curve. Does your system have that option? You can use that to set your own minimum speed for low temperatures, even if there is no particular place to set a "minimum speed".
 
Dec 30, 2020
4
0
10
0
Lots of current mobos have an option on the CPU_FAN header (and others) to set up your own "fan curve" - that is, the graph of what speed the fan should run versus what temperature is measured - rather than the default curve. Does your system have that option? You can use that to set your own minimum speed for low temperatures, even if there is no particular place to set a "minimum speed".
Not that I'm aware of. I just want to get this machine back to normal operation. Something has obviously been changed or gone wrong somewhere. It has worked fine for the last 3 years, this is a new development.
 

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