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Question CPU fan will only work from CPU OPT

TDHBP_Messed

Reputable
Dec 27, 2015
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I've helped my friend rebuild his PC with a new motherboard and so far everything was fine until we realized the CPU fan wouldn't work from the CPU_Fan pins and only the its RGB lighting would. We connected it to CPU_OPT and it worked well but we keep on getting an error and are prompted to press F1 to go into BIOS. It's fine from there since we can boot up using the boot options in the BIOS but it's inconvenient. The cooler in question is a stock cooler, Aspire from Ryzen 2700 and the motherboard is Asus ROG B450-F. We googled it before and it seems it was resolved for other people via a BIOS update but we did just that and it didn't work. There was another solution and that is it could be clogged with dust but how would it work on CPU_OPT if it was clogged?

Any help would be greatly appreciated and any info asked I will happily provide.

Also this is the error
https://prnt.sc/tc7kjr
 

Paperdoc

Glorious
Ambassador
The error message you get when the fan is plugged into the CPU_OPT header is just telling you there is NO fan speed being detected in the CPU_FAN header. Well, no, becausse the fan is not on that header! IFyou keep working this way, maybe you can go into BIOS Setup for the CPU_FAN header and tell it to Ignore the fan speed there, That will stop the error message.

As a test, try connecting any other fan in your case to the CPU_FAN header. Will that one work? If not, there are two possibilities: the header is faulty, OR it is configured oddly and needs adjustment. See your mobo manual p. 3-7. At the bottom there are a choice of settings and you should have that on "Standard". "Silent" or "Manual" might allow it to send the fan a low-voltage signal that fails to start it. "Turbo" or "Full Speed" should most certainly get the fan to start, but it will never slow down that way.
 

TDHBP_Messed

Reputable
Dec 27, 2015
105
0
4,710
11
The error message you get when the fan is plugged into the CPU_OPT header is just telling you there is NO fan speed being detected in the CPU_FAN header. Well, no, becausse the fan is not on that header! IFyou keep working this way, maybe you can go into BIOS Setup for the CPU_FAN header and tell it to Ignore the fan speed there, That will stop the error message.

As a test, try connecting any other fan in your case to the CPU_FAN header. Will that one work? If not, there are two possibilities: the header is faulty, OR it is configured oddly and needs adjustment. See your mobo manual p. 3-7. At the bottom there are a choice of settings and you should have that on "Standard". "Silent" or "Manual" might allow it to send the fan a low-voltage signal that fails to start it. "Turbo" or "Full Speed" should most certainly get the fan to start, but it will never slow down that way.
As I mentioned it's my friend's PC. The problem is he can't test any other fans because his current fans aren't even connected to the motherboard and the cables for that were missing, his fans operate completely separately so there's no way to test that. And thanks for the suggestion I will tell him to try it!

And we figured it out with the error message yesterday but thanks anyway :)
 

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