I can't figure out why the processor fan on my system doesn't work.

I have a D865PERLL motherboard. This model has four (3 pin) fan connectors, but only one is supposed to drive the processor fan. 3 of them don't work. The fourth does, but sure enough it is not the one designed to support the CPU fan. As a result, the fan doesn't turn fast enough. This means that I can use this PC, but if the ambient temperature is too high the fan doesn't provide enough cooling.

I thought the motherboard may have a problem, but on second thought this doesn't seem plausible. I would think that either all four fan connectors don't work or all of them do, but three out of four? Is it possible that this is actually an issue caused by the power supply? Can anyone suggest a way to figure out what is the cause of this?

Thanks a lot!

I doubt it would be the power supply. I don't see how a bad PSU would cause some fan headers to work, and others to not work. If you have a multi-meter you could try seeing if the other fan headers are putting out the correct voltages needed. If you get no voltage on the others then you know they are the problem.

The fourth does, but sure enough it is not the one designed to support the CPU fan. As a result, the fan doesn't turn fast enough.The fan header you choose has no bearing on how fast the fan spins, unless you have them individually set in the BIOS. Do you have SpeedStep turned on in the BIOS? And how did you find out which fan headers work and which don't? Does the CPU fan not spin at all when connected to the CPU_FAN header?

You can try resetting the CMOS, maybe a new battery, but if your system is overheating, I would contact Intel and get an RMA for that mobo!

Well, actually it does matter which fan connector you use. According to the mobo specs, the one fac connector that is different (it draws 3 times as much current) is the processor fan. The other three, although they look identical, provide a fraction of the power (by the same voltage).

I just connected the fan plug to each one of the four fan connectors available. One of them worked, the other didn't.

Don't know anything about SpeedStep, but I'll look into that.

Thank you for your help,

Franco

According to the mobo specs, the one fac connector that is different (it draws 3 times as much current) is the processor fan.That's odd. I wonder if only Intel mobo's are like that, or all Intel-based mobo's or what. I'm going to look into this...