I've recently built a home theater PC using some older components, and I'm having an issue with my Antec Flux Pro case fans. The PWM intake fans are locked at 100% speed, and I've connected them as instructed: the fans are linked to a hub, while the PWM lead goes to a motherboard header. Interestingly, the exhaust fan connects directly to the motherboard and is adjustable via the BIOS's Smart Fan 5. Despite trying all fan headers on the motherboard, the intake fans remain uncontrollable, and fan control software isn't helping either. The motherboard manual shows a strange pin configuration for the CPU and fan headers, leading me to suspect the intake headers might not actually support PWM. Has anyone encountered this problem? Is there a way to sort it out?
2 Answers
I checked the motherboard manual, and you're right; it does seem strange. Typically, 4-pin (PWM) and 3-pin (DC) fans share the same first three pins. Your fans should be GND, +12V, Sense, and Control. The fact that only the exhaust fan is controllable really stands out. It sounds like those SYS_Fan headers are not truly PWM; instead, they may be using a form of DC control. The "speed control" pin could be sending a variable voltage instead of PWM pulses for fan speed adjustment. You can usually control a single PWM fan or 3-pin fans, but a PWM fan hub is likely not going to work due to missing that 4th pin needed for PWM functionality.
It sounds like you're experiencing that classic headache with fan hubs. I suggest checking if the fans and hub are genuinely marked as PWM in their specifications. Sometimes the manuals have conflicting info. If they're supposed to be PWM, it's worth experimenting to see if they can work individually on the headers. You might find a solution there.
Absolutely! If they truly are PWM fans, then connecting them directly to the motherboard should allow proper control. Just be sure to check your BIOS settings too after reconnecting them.
That's frustrating! I had a similar issue. The first thing I would do is disconnect the fans from the hub and plug them directly into the mainboard's headers one at a time. It might help to verify if they can be controlled when not connected to the hub.