Help with modding a fan!

[jedimas729]

Hi all! Got another of my fun and interesting questions!!!! I recently came across 2 free 80 mm case fans but the only problem is that they are 3 pin and dont have molex connectors! Now ordinarily this isnt a bad thing but I am adding LEDs to my molex connectors and would like the fans to have the same thing done to them! The molex has 4 wires with 2 ground, a 5 volt, and I think a 12 volt? can I just cut the 3 pin wires and solder them onto a molex connector or is that second ground wire essential to the fan?

Oh I almost forgot, how do I identify which wire is which on the 3 pin? the colors are a red, a black, and a white! I unfortunatley dont have one of those output measurment thingies(multimeter?) and have no money at the moment to go buy one unfortunately:( ! So if someone could help me out I would really appreciate it!!!
Well once again thanks in advance! :D

[Starbuck3733T]

Pictures? text of label? that would help.

[jedimas729]

Pictures? text of label? that would help.I'll post them as soon as I get home, I am at work right now and have no access to a digital camera. They should be up by 8:30(2 hours from now) the latest!

[Darv]

Well the fan has a 12v line, a ground line and an RPM sensing line. The RPM sensing line won't work with a molex so you can forget about that one.

Then you want to add the 12v line to the yellow on a molex and the ground line to either of the black lines on a molex.

As ot which colour is which the easiest way is to try it and see. You could use a 12v battery or a computer PSU. I'm guessing that the white line is the sensor, the red is the 12v line and the black is the ground line.

It's different with each maufacturer though so you will have to test it to find out.

[jedimas729]

So I would just cut the connecter and then connect the 12v to a regular 12v battery? Man am I glad that I bought some of those for the last hurricane we had here! I'll try it out and if the red wire isnt the right one I'll just try the other wires till it works! Hope I dont shock the hell out of my self thats for sure!:D

[Darv]

Yep connect the 12v to the postive on the battery and the ground to the negative.

You will be hard pressed to shock yourself with only 12 volts. :wacko:

[jedimas729]

Hey you never know! Man I cant wait till I get home to try this out! Damn work and all its annoying ways!!!:D

[jedimas729]

Huzzah! I got it to work with a 9 volt and the red is the 12v and the black is the ground! Best of all: No Shocks!!! Heheh thanks for your help Darv!:D

[fivecheebs]

The RPM sensing line won't work with a molex so you can forget about that one.
Not nessecarily! You can have 2 terminals from the fan if you want to monitor the speed. You can have one for the power teminating in a 4 pin molex (red and black wires on the fan) and the original 3 pin to connect to the motherboard header (with the yellow and black wires from the fan) Someties you can get away with just the yellow for speed sencing iirc, i dont know if it depends on the fan or the mobo if speed sencing works without ground or not.

[toby]

i think you need the gruond but im not 100%

[Starbuck3733T]

You only need the ground if you do not have a common ground between the two. usually the ground on the PSU is common between the 3 pin fan headers on the motherboard and the 2 black lines in the power connectors off the PSU.

You can check with a continuity (multi-) meter. If theres continunity between the black on the PSU molex, and the ground pin on the 3 pin motherboard fan header, you do not need the ground. Otherwise, you do.

[fivecheebs]

You can check with a continuity (multi-) meter. If theres continunity between the black on the PSU molex, and the ground pin on the 3 pin motherboard fan header, you do not need the ground. Otherwise, you do.
Cheers star :) thats a good little tip there.

[Risky]

You can definitely get the rpm signal by just running that one wire to the fan header (as I have done in my rig). THe only problem is if you're using the 7V from the 12 and 5V line, then the rpm signal will be relative to 5V and probably not work.

[Starbuck3733T]

Cheers star :) thats a good little tip there.

Thanks. FYI, the reason that you need the ground if it isn't common is so you have a point of reference on the tachometer signal. without the ground, its just a voltage flopping around w\ no reference, IE useless. It will still register at 0 RPM, though (at least it has IME)

[fivecheebs]

Yea thansk mate, i understand perfectly. I did some experimenting a couple of years back with a mates fan/board (cant remember which mobo it was now) and his needed the ground. I have seen working without a ground with connected to the header before also, just didnt put 2 and 2 together to realise why.