Thread: Can 4 wire 120MM computer fan run on 12V pos/neg

Should do. From memory they used to work when we used two wire extensions to power them in pcs.

Hi Phillip

On a standard 4 pin molex connector Yellow is +12v, Red +5v and black negative. If there is a yellow tacho wire it will typically be to smaller 3 pin plug which plugs to a mother board header.

I've just had a look at a couple of old 120mm fans in the junk box with molex connectors and they have 2 wires into the connector with +ve to the yellow.

Cheers

Steve

Don't connect them the wrong way around cause it will kill the fan.

Now I am a little more confused.


If you look at the picture for these fans which I have as a front runner, there only appears to be a red and black to the fan itself ( down the LH side ).


I don't know whether there is another wire hidden behind but it appears not. Although a 3 wire fan has a yellow tacho wire according to Wiki.


I am unsure whether the power to the fan is preconditioned, like a digital stepper signal or PWM, or whether the fan can just run on the red as 12V DC + and black-.


4X 120mm 12cm Quiet Cooling Case FAN Ball Bearing Quality NOT Sleeve 25mm Wide | eBay


I just had another look at Wiki and it appears to me that these are just 2 wire fans that are wired into a Molex connector as a 4 wire fan will have 4 wires into the actual fan itself.
Anyone agree ,disagree?


Regards Philip A

That one won't work as is, as it's using the 5v line not the 12v line.

Simplest option is something like this 2 wire 12v fan, although the catch is it will always run flat out when powered

QZO 9025s 12V 0 2A Brushless DC 7 Blade Cooling FAN With 2 Wires 92x92x25mm | eBay

Ok thanks. I will have to try and find a 2wire in Oz at a reasonable price.


I just received 2 x80MM fans from China and one was completely destroyed and the other broken in half but gluable.
The vendor refunded but still a PITA.
Regards Philip A
I guess I could run an AB switch and power through a resistor I f I wanted dual speed , but I think one speed is OK.