[BIG EDIT]
My
Gigabyte GA-G31M-ES2L has a 4-pin CPU fan header. I recently purchased Arctic F12 and F9 PWM fans to use with it. Problem is, I can't get either to work properly.
I have Smart Fan control enabled in BIOS. But it reads 0 RPM for the CPU fan and appears to be spinning @ full speed. No Windows utility reads fan speed either.
Flashed to latest F10 bios. No difference.
If I switch back to my previous fan, a 3-pin Yate Loon D12SL-12 with a Zalman Fanmate, I can see fan RPM in BIOS and windows.
Using the same Fanmate and the Arctic fan, no RPM.
Switching back to the OEM Intel CPU fan (I didn't re-mount the whole heat sink, just connected the fan), which is also a 4-pin PWM fan, and it correctly shows RPM in BIOS and Windows utilities.
So at least I know my motherboard is OK!
Looking at the Arctic fan's leads, I notice that there's NO RPM SENSE WIRE from the fan to the main 4-pin connector:
![Image](http://img688.imageshack.us/img688/929/dsc0160lt.th.jpg)
Note the lack of a yellow wire feeding into that connector. But there's a RPM sense wire coming out of it! What the hell?
I bought these AC fans from Performance PC's, who sleeved them for free. Thinking that - maybe - Performance PC's screwed up when they sleeved them, I looked around online for photos of stock fans. In
this image, you can clearly see that the RPM-sense wire is not bundled with the other three. Instead it goes to a separate connector. I have these separate RPM wire/connector leads as well, but am at a loss as to how to incorporate them into the main 4-pin connector.