Question Asus x570-F cannot lower fan speed below 60&

[Thronsen]

Hi there-

I have the Asus Strix x570-F motherboard, where I have connected the 3 stock Fractal Define 7 chassis fans to CHA-1 (via the cases provided controller). The fans are 3 pin, ie not PWM. I cannot seem to get the fans to stop or spin lower than 60%.

In the bios I have set CHA-1 first through DC in Qfan Control. I clicked on manual and fan off, and pushed the sliders up 50 degrees before the fan should come on. I have monitored the temp, which never goes above 42, yet the fans spin all the time at 60%.

After that, as a test, also in the bios I set CHA-1 to PWM (I know they are not PWM fans). This had the effect, while I was in the BIOS, of the fans running much lower than 60% (and at an acceptable volume). As soon as I enter windows however they spin back up to 60% (where the produce noise I am trying to eliminate).

I would appreciate any suggestions or advice. The fans are obviously capable of spinning less quickly, but I cannot seem to get them to do so.

Thanks.

 

[Thronsen]

Bump. Any help would be greatly appreciated. Thanks.

 

[Karadjgne]

You won't. 3pin fans are voltage regulated, they'll generally run at 5v-12v or 7v-12v, and that all depends on the fan and just how much voltage it requires in order to spin. If you figure 12v is a 100% duty cycle, that puts 5v at @ 40% or 7v at @ 60% duty cycle. Your inability to get lower than 60% is due to your fans requiring at least 7v in order to have enough energy to spin.

PWM is different in that its a constant 12v, the pulse width modulation is nothing more than a specific timed on/off period. So at 100%, you have full 'on', but at anything less you are in a constant state of trying to turn on full, turns off, turns on etc. This allows pwm fans to go as low as @ 20% duty cycle for some fans.

 

[Thronsen]

Hi Karadjgne-

Thanks for your reply. I appreciate why the 3 pin fans cannot spin below 60%. But shouldn't the fans be able to spin at 0%, ie with the motherboard running no power to those fans? It seems there are setting for this in the BIOS (at least at certain temperatures) but I have not been able to use that feature in practice.

Any more thoughts would be great. Thanks again for your help.