Plugging in case fans


Active Member

I'm putting together my HTPC.

I've noticed that the case fan (the fan from the Silverstone LC02 case) has a three pin socket on the end of it.

Whilst the motherboard SYS_FAN socket has four metal legs.

Now the three holes in the plug will fit the 4 prong connector- one is just left unconnected, and there are little plastic lugs on the back which force you to use the first three prongs.

So would I be right in assuming I can just plug the fan cable into the SYS_FAN socket with one prong unused and everything will be OK??

I assume that the unused one is speed control or something like that.

I'd appreciate some advice.


Distinguished Member
Yes, the fourth prong is for speed control by varying the voltage.
This just means your fan will run at full speed.


Active Member
A 4 pin header allows the fan to be controlled with PWM - and intel specification ( basically stops 'stalling' at very low speeds) - The above post is incorrect though, a 3 pin header will allow fan speed control, but it will be via voltage rather than PWM.

In short, 3 pin will be fine and your mobo will likely control the speed of the fan based on case 'mobo' temp with an onboard sensor.

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