Question Fans connected to fan hub, but they run at max speed despite all of them are PWM?


Nov 19, 2015
Fans: Lian Li Bora Lite 120

Fan Hub: Cooler Master Masterfan PWM Hub

Motherboard: Gigabyte B550 Vision D

I have ten of the named fans connected to the fan hub, which the hub connects to the motherboard with a proprietary 4-pin cable with two wires (see in spoiler). The fan hub is powered by SATA cable. The Sys_Fan headers on the motherboard are 4-pin; I have accessed the BIOS to set all Sys_Fan headers to PWM mode.



That cable in your "Spoiler" photo looks OK, but let's just check a detail. It has 2 wires. On one side of the connector body there are two ridges, and these must fit on either side of the plastic "tongue" that sticks up beside the mobo SYS_FAN header. Looking closely at that connector, one of the wires should be OUTSIDE of the space between the two ridges (that is for Pin #4, the PWM signal pin). The other wire should be just inside that space, for Pin #3, the speed signal wire. If that is how the wires are in that connector, then be sure you plug it into the mobo SYS_FAN header correctly with the two ridges down its side fitting around the tongue of the header.

Next, ensure that the other end of that cable is plugged into the correct port, and in the correct orientation, on the end of the Hub. It does NOT go into one of the numbered OUTPUT ports that are for fans. Make sure it is in that port snugly, because it sounds like your Hub is not receiving the PWM signal it needs from the mobo.

In the configuration of the fan header you are using, you tell us it is configured for PWM Mode, and NOT for Auto Mode. I assume also that is is set to use the normal automatic fan control strategy or Profile, and not set to run in Turbo Profile or some such.