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View Full Version : How to reverse polarity on case fans?

XyBeRz
03-25-2006, 03:53 AM
Does anyone know how to change the polarity on case fans? My fans have 3 wires, one blue, one red, and one black. I wanted to ask someone who has done this before just in case.
zip
03-25-2006, 06:10 AM
As far as I know, if you invert the Red one with the Black one you'll get the desired rotation.But the Blue wire is tricky , it might be a Sensor or if the Fan is Brushless there is no way to change the way of the rotation, unless you turn the fan around.Brushless fans need an extra wire or circuit so that an impulse tells them in which direction they should spin......that is what I think the Blue wire is....
fstroupe
03-25-2006, 10:14 AM
The third wire is for RPM monitoring, some are blue, some are yellow. It is much easier to just turn the fan around, that's why there are screw holes in both sides, excepting some specialty fans.

But, if you are dead set on changing wires, as zip said, just reverse the red and black.
XyBeRz
03-25-2006, 01:19 PM
As far as I know, if you invert the Red one with the Black one you'll get the desired rotation.But the Blue wire is tricky , it might be a Sensor or if the Fan is Brushless there is no way to change the way of the rotation, unless you turn the fan around.Brushless fans need an extra wire or circuit so that an impulse tells them in which direction they should spin......that is what I think the Blue wire is....

The fans that I'm trying to reverse are single 120MM ball bearing fans. Sorry, I should have been more descriptive with the wiring on the fans. They have three wires coming from the fan itself, which is:
Black, Red, & Blue (In that exact order)
and end at a 3 pin female connector which have all three wires connected.

Then there is the 4 pin molex power cord, and at the other end is the 3 pin male connector and to that side only the red and black wires are connected.

I don't know if that makes a difference or not that the male 3 pin connector has only the red and black wires connected and that runs to the 4 pin molex.
kcaverly
03-25-2006, 01:41 PM
It just means that you won't have RPM monitoring. If you plugged the 3 pin into the mobo you could monitor RPM's and change speed with something like Speedfan
silenze
03-25-2006, 02:49 PM
It's easier to just turn the fan around..

Don't know if reversing the wiring will work, I believe most if not all fan motors are designed to spin in only one direction and won't function when wired reversely...
XyBeRz
03-26-2006, 12:56 AM
It's easier to just turn the fan around..

Don't know if reversing the wiring will work, I believe most if not all fan motors are designed to spin in only one direction and won't function when wired reversely...

Well you see, the only reason why I posted this is because my fans are Evercool AL12025 120MM fans that are all chromed with an aluminum housing. On one side of the fan, it's all crome, and the other side has a big white sticker in the center along with a white bracket that holds the fan blades. I want the chrome side to show up not the sticker side.