I recently rebuilt my PC using a Fractal North case and, to keep everything organized, I opted for PWM splitters for my fans. Currently, my chassis fans are connected to a powered Noctua NA-FH1 fan hub that plugs into a chassis fan header on the motherboard. My AIO radiator fans, on the other hand, are connected through a basic (unpowered) PWM splitter to the CPU FAN header. The AIO pump is plugged into the AIO PUMP header. However, when I checked the BIOS, I noticed that all my fan speeds are showing as "N/A," except for the AIO pump. If I connect the fans directly to the motherboard headers, their speeds are detected just fine, but when they're connected through the PWM splitters, they're not recognized. The fan control works, and they ramp up under CPU load, but I can't see their current speeds in my monitoring software. Is this typical behavior with PWM splitters, and is there a better solution?
3 Answers
The motherboard can typically only read speed data from one fan, so make sure you're using the designated main fan port on the fan hub. If your Noctua hub has a connector labeled '1', that's the one you want for speed reporting. For the dumb splitter too, look for the connector that acts as the main signal; without that, speed won't be detected.
Make sure that one of your fans is connected to Port 1 on the Noctua hub. That's the port that sends speed info back to the motherboard. If nothing is plugged into Port 1, that's probably what's causing the issue you've noticed—no speeds will be reported then!
That did the trick! I checked both splitters and connected a fan to Port 1. Thanks a lot!
Check the splitters' connectors; one of them should have the third pin (for tach signals) while the others should be missing it. The motherboard can read speed from just one fan, so if all connectors lack that tach pin, none will report speed. You might want to refer to the hub's manual—or lack thereof, haha! Just remember, the output labeled '1' is your go-to for tach signals.
No manual came with mine, but I figured it out! I reconnected a fan to Port 1 on the Noctua, and the same for the other hub; that sorted out the detection issue. Thanks!
I’ve been using Corsair and Lian-Li for so long that their hubs manage this automatically! I switched a fan to the correct port, and it worked perfectly. Thanks for the help!