3 Pin Fans for Dummies

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rls669

Limp Gawd
Joined
Jun 5, 2004
Messages
462
Here's a noob question: what does the 3rd wire do? Does it just send the rpm signal? Can you just hook a 3 pin fan to power and ground and not use the 3rd wire?
 
Power - red
Ground - black
RPM sensor - white/yellow most of the time

And yeah, you don't need the RPM sensor. You can cut if off if you want.
 
Yeah the 3rd is the sensor and isn't needed. If you have a 3pin - molex adapter for example that 3rd wire won't be hooked up.
 
Okay, here's another question: say I have a fanbus that displays rpm, and a big 3-pin fan that's beyond its rated power. Could I hook the fan power and ground to the psu, but run the rpm wire to the fanbus input to show the rpms? Or would that earn me a nice puff of smoke?
 
No, but I haven't tried it yet. When I do, it'll be with a spare psu with the pins shorted to run on its own, just in case.
 
It will work perfectly fine running the power from a molex and sending the rpm signal to either the motherboard or the fanbus. I have a couple fans in my computer that are running through a fan controler and then the rpm sensors connected to the motherboard. If you do a search online you can even find premade connectors to connect to your 3 pin fan connector and will already be split, molex for power and 3 pin header for rpm.

http://www.crazypc.com/products/5407.html

above is a link to such a cable.
 
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