Help with fan mod

[Hansemannen]

Fan mod
I'm going to try mod my 360 with one more fan on the side of the xbox, like a 80 or 120mm fan. The tought was to connect it with the air conductor to the cpu. (the plastic thing that leads the air to the cpu) The first question is if anyone knows how the standard fans speed is changed. Are they 12 or 5V or is the voltage variable? And might I grab power from the standard fan connector or should i use the "missing fan connector installation"-guide and take power from that source?
The mission is to make the xbox quiet! Lower the speed of the original fans or exchange them and have one more fan to help cooling. 
And of course I will show some pictures when i'm ready.. Grateful for all kind of tips
//Hasse

[gigabite]

The original fans in the Xbox 360 increase speed when the temperature gets hotter.  Don't draw power from that source, use this (http://www.freepler.de/userdaten/38928917/download/xbox360/fan_connecter_tutorial.pdf) and you can get 5v or 12v.  You can increase the stock fans speed to 12v by connecting it to a 12v point or make it go to whatever voltage you want by connecting it to various other points.  You also can change it so that one fan is at full speed (or slow) and the other is slow (or at full speed).

gigabite

[Cynical Jawa]

What gigabite said - do not draw additional power from the existing fan header - it can't supply the additional current.

Just out of curiosity, does the 360 vary the fan speed by altering the input voltage or the ground voltage?

[Hansemannen]

Alright, i'll see how it will be done   but is it possible to lower the power input to the original fan with some kind of resistor or something like that. How many Ohms should that be?
//hasse

[gigabite]

It is possible to lower 1 (or both) speed/s of the fan/s by connecting them to alternative power sources (i'll be releasing soon a picture of all the different power sources like 3v, 5v etc) on the motherboard.  You could connect the fan to (for example here) a 12v source but in between have a resistor to lower the voltage but why not just connect to the point which already has the voltage you want? (there are lots)

gigabite