Question Chassis fan speed at 99% = 1500 rpm and at 100% = 2200 rpm, what is happening?

[KBDMB]

My PWM chassis fan is acting weird. I think this issue excisted since the beginning but i just noticed it when installing new case fans. When in Argus Monitor setting the curve, or any other program. The fan doesnt spin below 45%, and between 45% and 99% it gradually ramps up to 1500ish rpm and at 100% goes full mad up to 2200 rpm. I would really like to control the last 700rpm as well. Any help is appreciated , thanks! kind regards.

 

[Starcruiser]

What motherboard and fans are you using? You may need to switch PWM mode to DC mode to get more control depending on the board.

 

[KBDMB]

I have a ASRock z390 Phanton gaming itx/ac mobo and the fans are Be Quiet Silent Wings 3, the bios does not give an option to change the fan control mode on the chassis fan header, it seems like it only runs in PWM mode, i might be wrong here.

What could cause this behavior in a fan besides the control mode? is it a power issue? the header should provide 12v. im kinda lost here.