Hey i have just built my new system, and all the fans that i ordered from e-bay, are coolermaster 120mm with a 3pin female connector.
My motherboard only has one sys_fan header and i want to power these 4 fans. Can i cut the 3pin plug off the van and simply wire the red/black wires to a molex plug? Ignoring the speed control wire which i'm guessing is the yellow one?
I have found heaps on the net to change a 4pin molex to 3pin sys_fan header plug, but not the other way round. Any clues?
In theory that should work, but I'm going to be honest here, I've never tried that, so I can't say for sure. (I've never had shortage of mobo 3-pin, and even when/if I did, I had 4-pin molex fans)
What I can tell you for sure. Is that my 4-pin molex case fan, has the wires spliced into an extension as follows:
Fan | Molex
n/a ---> Red
n/a ---> Black
Black ---> Black
Red ---> Yellow
As you can tell from the left column, the fan has two wires leading directly to the power supply's molex. What I find interesting, is that Red matches with Yellow, and NOT with Red on the molex side.
My fan has an extension (Male to Female Molex adapter) and that why it has to be spliced. However, if I were you, and I had no such adapter, I would rather avoid having to unsheath a brand new power supply's wires. Instead, I would plug the 2 fan wires directly into the 2 molex holes. The disadvantage is you might need 3 separate molex plugs, which only leaves 1 for your IDE device(s). With some luck though, perhaps you can fit 2 sets (4 total) of fan wires to 1 single molex (the fan wires are very thin, and the holes are quite wide).
Of course, that's probably what you're planning on doing anyway?
Basically i was not going to detach any wires from the PSU, i was simply going to make my own molex cable with 4x molex 4pin sockets, and cut the 3pin plugs off the fans, and simply wire the power and earth into the molex plugs. Then i can plug one end of my adapter into a molex off the PSU and run the 4x newly molexed fans off my cable. The only thing is i will loose speed control, they will run full speed forevor