PWM fans seem to be running at 100%

[andrewjs18]

hi all,

I'm new here so go easy! I just finished up building a brand new system where I have 5 arctic F12 PWM fans installed. 2 of the 5 fans are hooked up directly to the fan header on my motherboard (gigabyte Z170XP-SLI-CF) while the other 3 are hook up to an akasa flexa FP5S fan splitter.

The 3 fans that are connected to the fan splitter seem to be running at 100% (~1,500 RPM, per the BIOS) constantly, even if I set the fan to run in silent mode in the BIOS.

I'm not entirely sure what's going on here. defective splitter? defective fan? I'm running windows 10 and my BIOS was just updated to latest version available as I thought maybe the previously installed BIOS was buggy or something.


fans: https://www.arctic.ac/us_en/arctic-f12-pwm.html
fan splitter: http://www.akasa.com.tw/update.php?...ype_sub=Fan Cable Adapters&model=AK-CBFA07-45


any help is appreciated!

 

[aigomorla]

best way to find out is by moving some of the fans over to the working splitters to see if that changes to speed on the fans which always ran 100%.

If thats the case, its a bad splitter.
If thats not the case, then its a bad fan.

 

[BonzaiDuck]

I couldn't be sure about the Gigabyte boards, but I'd come across mention of an ASUS board and an AIO cooler recently -- probably a Corsair.

As I recall (my caveat to what I actually remember), the issue was resolved by using a different CPU_FAN header -- if there are indeed two: CPU_FAN and CPU_FAN_OPT. One is able to adequately control pumps, and the other one isn't.

How this might play out using a PWM splitter, I cannot say. You would think that such a splitter connected to the right fan port would control the pump and fans such that the pump is running at the appropriate speed for the appropriate temperature.

But that's just what I remember, and if I'm wrong -- I plead "not guilty."

If the fans are PWM enabled, you should be able to set a "fan curve" with the control software so they all ramp up to 100% at the hottest CPU temperature and then drop off as the CPU cools down.

Did you install the Windows fan-control software for the Gigabyte board? I wouldn't know if Gigabyte provides an encapsulation of the fan-control feature within the BIOS, but for ASUS boards, there is a "User" option in the BIOS which corresponds to a setting made in the Windows software.

 

[ClockHound]

Is the splitter connected to the CPU fan header too? In my experience with Gigabyte boards, only the CPU header is PWM, the other headers while being 4pin are running with voltage control, not PWM. Stopped using Giga boards for that reason alone.

The symptoms you describe are expected when a psu-powered PWM splitter is connected to a 3pin header. The header attempts to control the voltage, but the psu is supplying 12V to the fans and there is no PWM signal to modulate the 12V.

Simple test: Connect the splitter to the cpu header and connect all the fans to the splitter - ensure the PWM signal cable from the splitter is connected to the cpu header.