Question B450M-A PRO MAX, SYS_FAN1 PWM control not working.

[ehm_three]

I've had this motherboard (B450M-A PRO MAX) since October 15, 2020, and I've had issues with the system fan header not being able to control the fan speed via PWM, all fans remain at a constant speed. I've gone through the usual steps of updating the BIOS and trying different fans. I initially had a 5-pack of Arctic P12 fans, later swapping them for 6 Corsair RS120s.

I used to use an Arctic 10-Port PWM fan hub, I have tested the fans both with and without the fan hub installed. I have tested with a single fan connected to the header and I'd still have no luck with it responding to PWM control. Even just daisy-chaining all the Corsair fans into the header doesn't change the speed. It does measure the RPM of the fans installed, I can manually slow it down with a finger and it reads correctly. I'm worried I may just have a faulty header, or that it decided to die on me after 4 or so years.

Additional Info:

• The CPU PWM control works fine, it follows the curve I've set in both BIOS and FanControl.
• I have tried both MSI Center and FanControl to try and tweak the system fan speeds. No luck.
• Even with Smart Fan Mode off, I cannot set the fan speed to something else, it seems to be stuck running at a constant speed.
• I've also reset the BIOS twice, once by applying the default settings. Second by removing the CMOS battery.
• I've also tried setting the temperature source to either the System or the CPU.

Any help would be greatly appreciated, my PC sounds like a Playstation 4 with how the fans are running on max.

 

[Lutfij]

Welcome to the forums, newcomer!

First off, if I were in your shoes, I wouldn't have paired a Ryzen 5000 series processor with a motherboard that has a lackluster VRM design.

That being said, have you tried reflashing the BIOS on the motherboard? If the BIOS is what's corrupt and your platform conks out, then you're either going to need a CH341A BIOS programming toolkit or a BIOS chip meant for your motherboard or a new motehrboard.