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

[PhilipA]

I am designing a mount for a set of fans to sit in a window of my D2 to expel hot air .
I have ordered 3x80Mm computer fans which are 2 wire but I am not sure they will be man enough.
120Mm fans are an option but most seem to be 4 wire Molex connector.
I understand that the 4 wire has 12v pos/neg plus a yellow tacho wire to give feedback to the ECU and the 4th wire gives a PWM voltage to vary speed based on temp.
I just want to make sure that the fan will work with just 2 wires ( red and black) connected.


Any one know?
Regards Philip A

[Rig110]

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

[Rok_Dr]

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

[101RRS]

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

[PhilipA]

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 (http://www.ebay.com.au/itm/310761102693'ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649)


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

[FeatherWeightDriver]

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 (http://www.ebay.com.au/itm/QZO-9025S-12V-0-2A-Brushless-DC-7-Blade-Cooling-Fan-with-2-Wires-92x92x25mm-/131050713363?pt=AU_Components&hash=item1e833b3113)

[PhilipA]

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.

[incisor]

i sell em by the box load to some caravan repair guys

they put them behind fridges and the like...