Question CPU Fan header problem

[FFGnz]

When I first booted my newly built pc, I noticed that the CPU fan was not spinning continuously, spinning and stopping repeatedly. I first suspected the problem might be caused by the fan. However, when plugging the CPU fan into the SYS Fan header and the rear fan into the CPU Fan header, both were spinning continuously. That made me think the problem might be the CPU Fan header's fourth pin, since the CPU fan has 4 pin connectors and the rear fan I used for the tests only has three.
Has anyone ever had a similar problem? I plan on contacting the motherboard manufacturer to ask for a warranty coverage on the product, but I wanted to make sure that the motherboard is indeed the problem so any insight and ideas are really appreciated.

The setup I'm using:
Motherboard - GIGABYTE B550M Aorus Elite
CPU - AMD Ryzen 5 5600X
CPU Fan - AMD Wraith Stealth

 

[Karadjgne]

How many wires on the cpu fan connection. Should be 4. In bios, go find your cpu fan settings, make sure its set for pwm not auto or dc/voltage. Raise the minimum duty cycle or % above 20%.

 

[FFGnz]

How many wires on the cpu fan connection. Should be 4. In bios, go find your cpu fan settings, make sure its set for pwm not auto or dc/voltage. Raise the minimum duty cycle or % above 20%.

It does have 4 wires. I set the cpu fan control to PWM, but that didn't solve the issue. I noticed that the fan works continuously at around 200~230 RPM when the speed is lower than 70%. When it hits 70%, the fan spins up to 200 RPM and stops after a few seconds, spinning again and repeating that.

 

[Unolocogringo]

Have you calibrated the fans in the bios?
My new ml140s were weird until I calibrated them in bios..
200-230 rpm@ 70% or below speed is way off the mark. Should be 2000-2300 for 70%.
Could be fan or motherboard, but before you RMA the motherboard you should find out which part is the problem.

 

[Karadjgne]

Seriously sounds like pwm fans set on DC. Are you positive the fan is actually in cpu_fan header? Many mobo's have a cpu_alt or even a aio_pump header right under/next to the cpu_fan header.

 

[FFGnz]

Seriously sounds like pwm fans set on DC. Are you positive the fan is actually in cpu_fan header? Many mobo's have a cpu_alt or even a aio_pump header right under/next to the cpu_fan header.

Yes, the fan is in the cpu_fan header. And I've also confirmed it's set as PWM. The CPU Fan control mode doesn't seem to affect the weird behavior of the fan. The only thing that changed it was when I changed headers with the rear fan, where both worked properly, and the cpu fan was spinning at 800RPM continuously.

 

[FFGnz]

Have you calibrated the fans in the bios?
My new ml140s were weird until I calibrated them in bios..
200-230 rpm@ 70% or below speed is way off the mark. Should be 2000-2300 for 70%.
Could be fan or motherboard, but before you RMA the motherboard you should find out which part is the problem.

I'm not really sure how to calibrate them. All I see in bios when I open the fan settings are some options like: Temperature Warning, CPU_FAN Fail Warning, CPU_FAN Speed Control, Fan Control Use Temperature Input, Temperature Interval, CPU_FAN Control mode and CPU_FAN Stop

 

[Unolocogringo]

After looking at your manual it appears you need to install their app center . Along with Smart Fan 5 app to be able to calibrate and control fans.

 

[FFGnz]

so.. I ran some more tests, and I'm starting to believe the problem is the fan after all. I was able to control the fan speed in bios, and realized that the fan was spinning up to 800 RPM when the speed was set to around 40%. As it approached 50%, there were fluctuations in the fan speed, varying between 800RPM and 350RPM. From that point on up until the 70% mark it stays continuous at 200RPM and above 70% the fan repeatedly stops and goes back to spinning. This makes me think that the reason the fan was working when plugged to the SYS_FAN header was simply that it was being used at less than 40% speed. I might try seeing if I can get another cpu fan to make some final tests.