How to Make a 4pin Molex-to-3pin Converter Cable
Introduction:
I had bought a fan controller a while back that allowed controlling fan speeds for fans with a 3pin connector. But the case I have came with 2 large fans that may be proprietary and they have 4pin Molex connectors. I sought help here on the Overclockers forum for some helpful info, which I got very quickly.
NOTE: The reason why in some steps it shows the electrical tape on the female Molex connector and others it doesn't is because I didn't think of making the guide until after I already finished it.
Tools that I used:
Angled Pick
Wire Cutters
Pliers
Needle-nose Pliers
Flathead Screwdriver
Scissors
Electrical Tape
Wire Crimpers
1. I have a bunch of old unused fans, so I took the one that I liked the least and cut the 2 thin wires as close as I could to the Molex connector. (circled green in the pic below)
2. Since I was reusing a connector from a old fan, there were 2 extra wires leading into the 4pin Molex connector that I wanted to remove. For assurance nothing would short and to look nice. To do this, I took the needle-nose pliers and using only the one side of the pliers, I pushed in the 2 pins that were sticking out and preventing the pin from falling out. Note: This only has to be done for the 2 pins that have the 2 thin extra wires running to them.
Also, this doesn't Have to be done. You can use any way you want to prevent the wire from touching anything else and shorting something out. Even wrapping it in Electrical Tape is fine.
After that that, it should look like this -
And to ensure nothing touched those 2 very small wires, I wrapped it in some electrical tape, like so -
3. Looking back at the pic in step 1, there was a Female and Male Molex connector.Instead of wasting the male connector and pins, I reused those later. Use the needle-nose pliers to get the big Molex connector off by pushing those fin-like metal pieces in, like in step 2, and then cut the wire close to the male pins.
(The male Molex connector is unused, do as you want with it, but keep the 4 pins)
So now we have this (I twisted those 2 black wires together to make the 6th step easier)
I decided to make this guide after I actually did this, and forgot that the pics I had taken already had crimped wires. The 4 wires coming from the female Molex connector should be crimped, about 2mm less than a cm.
4. Step 4 is simple. You know those 4 male pins we saved from the Molex connector? We are gonna reuse them soon. Cut 3 of them where I marked it in the next pic with the pink line and green arrows -
This piece can be a bit sharp after cutting it. Though I'm sure anyone that owns wire cutters would know.
5. Now that those pins were cut, you have this little cylinder of metal with a opening down the side.
I took my flathead screwdriver and shoved it into that spot, like so -
I did this on both sides, to spread it out and make it easier to work with, because the wire coming from the Molex connectors was much thicker than the fan wire.
6. Now you need your 3pin connector. You can get this from a old fan if you have it, or even buy one. (of course you would just buy the converter before buying the cable to do it yourself lol)
Cut the wires from the 3pin cable, leaving as much wire as possible, or if you are going for a exact length and have everything measured out, cut it however you like. And then, crimp off the plastic where you cut it, about 2mm less than a cm
7. We now have those male pins opened up enough to easily put wire inside of it. Maybe there is a better way of doing this next part, but how I did it and how it worked first try, I took one of those opened male pins and first laid the smaller fan wire in it and then the thicker Molex connector wire on top.
Black (ground) wires go to black. The Red 5v wire coming out of the female Molex connector goes to the Yellow RPM wire on the 3pin connector. and the Yellow 12v wire from the female Molex connector goes to the Red 12v wire on the 3pin.
This is a pain btw ^, haha. After that, I took my pliers and I squeezed the sides together as hard as I could with my hands, to ensure nothing would come loose. After that, I wrapped the 3 connections in electrical tape. Make sure to do this and make sure there is no wire or metal touching from other connections. They need to be separated or it could cause problems and something could short out.
Here are my 3 connections wrapped up in electrical tape -
8. As the final step, I wrapped the 3 connectors in a small amount of electrical tape, to further ensure that if I tugged on it, that nothing would come loose. Camera flash really makes things seem dustier than they are haha.
Here is a video of me testing it out on a old motherboard and fan (It's a phone camera, they do bad in low light) -
Special Thanks to the following Overclockers.com forum members for providing help and info:
Boulard83, Conumdrum, thideras, jaymz9350
If anyone needs help or has questions, feel free to ask. Enjoy.
Also, there is more info found here - http://www.overclockers.com/forums/showthread.php?p=7404793#post7404793
about places to purchase the stuff. It's on the first page, I don't want to steal someones links that they commented.
WARNING:
Last edited:
. I know just the basics about this stuff. I'm sure there is some way to discharge this thing, maybe even Google would tell me. But life > little sound. The weird thing is, there is a knob to control the fan/s. There is 3 fans in this PSU. 2x 80mm and 1x 120mm. I'm not sure if each one is controlled by the knob, probably just the 120mm. 
