So, I keep seeing that you shouldn't plug into this slot. I have it plugged in, it runs perfectly fine. HWMonitor shows all 5 fans, and all their RPM's. So.. What's wrong with the PWR_FAN connector again..?
Pwr_fan was designed to allow you to monitor PSU fan RPMs. All of the mfrs that I know of have still supplied a constant 12V to the header so it can power a fan. The only issue is that there is you can't control the voltages on the header to reduce fan voltage. This means that the fan will always run at max speed...and noise. If your fan is working and the noise level is acceptable for the fan, then you are good to go.