I bought the components second-hand and am trying to determine whether my MSI B450I AC motherboard is faulty. A 4-pin Thermalright TL-9015 PWM fan is connected directly to the CPU fan header, with no splitter or hub. I enabled Smart Fan Control, selected PWM mode, chose the CPU as the temperature source, and configured the curve at 0, 20, 65, and 80°C with fan speeds of 20%, 35%, 75%, and 100%. However, the fan remains around 1000 RPM regardless of temperature or the selected curve. I also tested the system-fan header and other Corsair 4-pin PWM fans, with the same result. Switching the headers to DC mode makes the fans stop completely. I removed other fan-control software and only have Core Temp running in Windows. Is there another BIOS setting or hardware issue I should check before returning the motherboard?
3 Answers
First check whether 1000 RPM is simply the fan's minimum controllable speed. Some fans will not respond to very low PWM duty cycles, but setting the curve to 100% at every temperature should still make a noticeable difference. Since multiple known-good 4-pin fans behave the same way on both headers, the motherboard, its BIOS configuration, or the PWM signal is more likely than the individual fan.
The temperature curve matters, so confirm the target temperatures are above the current CPU temperature. Still, forcing every point on the curve to 100% is a useful test, and if the RPM remains unchanged then this is not just an incorrectly tuned curve. Check that the connector is a true 4-pin PWM plug with the pins aligned correctly, and test another header or fan before concluding the board needs to be returned.
Make sure the fan is actually detected in the hardware-monitoring page and that the changes are saved after leaving BIOS. It may also be worth loading BIOS defaults, updating or reflashing the motherboard BIOS, and then configuring only the CPU fan header for PWM control. Fan-control software will not help if the motherboard is not exposing the headers correctly; testing from a freshly reset BIOS with no Windows fan utility installed should help isolate the problem.
Related Questions
Lenovo Thinkpad Stuck In Update Loop Install FilterDriverU2_Reload