CPU_Fan doesn't work on Asus strix B350-F

nikosp420

Prominent
Jan 20, 2018
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510
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I bought the Asus strix B350 F yesterday and came with bios 3203 . My cpu_fan was working fine. i updated to 3401 bios and my cpu_Fan stopped working.It doesn't boot as it says CPU fan is not connected or N/A.Fan is working cause i tried CPU_Opt and its working on 2700rpm.Also my PSU is 850w so it has plenty of electricity.
So far I tried :
1)Connecting to cpu_fan and setting low RPM to 200
2)reseting cmos by removing battery or using a metal object on CLRTC
3)Downgrading bios to 0902 and 1001 but it doesnt let me downgrade

Now my pc is working as i set bios to ignore cpu_fan and setting my fan on cpu_opt. is there a problem leaving it on cpu_opt? QFan doesn't let me adjust rpm on cpu_opt.

P.S. my processor is AMD Ryzen 5 1600 with its stock wraith fan
 

DRagor

Illustrious
Soooo ... 3-pin case fan was spinning when connected to CPU_FAN header? But CPU fan connected to same header will not spin? If the CPU fan is 4-pin, that could mean a 4-th pin on header is not working. Since this pin is responsible for changing speed on 4-pin fans, it would explain why the CPU was not working. I'm not sure if your board allows changing CPU_FAN header to DC controlled in BIOS, but if it does, I would switch it to DC mode and connect CPU fan there. If it will make it work, that would confirm 4th pin failure.
 

helpstar

Polypheme
try resetting the BIOS again, be sure the fan connector is correctly plugged in.

disconnecte the power plug from the wall, press the power button for about 5 seconds and shorten clrtc for about 5 seconds too. Try powering up again

eventually load default BIOS settings

update the BIOS 3401 again in BIOS with EZ-Flash
 

nikosp420

Prominent
Jan 20, 2018
3
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510
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even 3pin fans can work on cpu_fan header?? and also reflashing 3401 bios on top of 3401 can fix this issue??

 

DRagor

Illustrious


3-pin fan will work on CPU header if the header is not broken.
Re-flashing will only help if the problem was caused by failed flash - however it will not help if the problem is of hardware nature (header dead) or if it is caused by new BIOS version directly (in which case it would affect anyone applying this BIOS update).
 

nikosp420

Prominent
Jan 20, 2018
3
0
510
0
Ok! So, as far as i have checked both cpu_fan header(i checked with 3 pin) and CPU fan works(i checked with cpu_opt)! so i have no idea whats wrong.. i did what helpstar told me :

but had no luck!
So if both works why i cannot get them to work together? what else should i do?

 

DRagor

Illustrious
Soooo ... 3-pin case fan was spinning when connected to CPU_FAN header? But CPU fan connected to same header will not spin? If the CPU fan is 4-pin, that could mean a 4-th pin on header is not working. Since this pin is responsible for changing speed on 4-pin fans, it would explain why the CPU was not working. I'm not sure if your board allows changing CPU_FAN header to DC controlled in BIOS, but if it does, I would switch it to DC mode and connect CPU fan there. If it will make it work, that would confirm 4th pin failure.
 

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