Build an External Fanbus

You may have seen different variations of what’s called a “fanbus” in articles, other people’s systems, or you may even use one yourself. I myself use two different versions: One of my own design, which has a bank of connectors on the top, and another (in the more traditional style, grasshoppa…) which has a smaller bank of connectors on each side.

Now, I also have a monitor fan, and I plan on buying a second, just for that little bit of extra cooling, and because I can’t mount one right in the middle of my monitor.

If any of you have a monitor fan (I got mine from 3DCool), you’ve probably noticed that the power connection is a molex connector mounted on a backplate. Maybe I just got a bad one, but the first time I plugged it in, the pins bent and got shoved out. As a temporary fix, I positioned the pins correctly and filed the connector from behind with epoxy.

This solved my problem with the pins, but what if I wanted to add another fan (like I plan on doing) or any external 12V appliance (whatever that may be)? Not only is that connector kinda ugly, but it doesn’t leave much room for expansion.

Case Rear

Ergo, I decided to build an EXTERNAL fanbus.

Basically, it’s nothing more than a blank backplate with 3 (or 4 if you want) RCA connectors instead of the single molex. This is a very easy project to do, so I would think anyone can do it.

One thing I had that made it VERY quick and easy is a drill press. If you’ve got a drill press, you don’t have to worry about punching the holes and then drilling, since it pushes the bit straight down, and there’s no risk of it “creeping” before it punctures the metal. It’s also a major help for case modding.

Anyway, back to the original subject. I bought a pack of four female and a pack of six male RCA connectors (make sure you get the solder type male connectors), a butane heat gun and a lot of shrink wrap tubing – all at RadioShack.


For the back plate, I used a ¼” drill bit on the press and set the plate flat on a 4×4 board (gives a secure platform to drill into that’s pretty much disposable). I neglected to measure exact locations for four holes on the backplate since it was easy enough to eyeball it. Now that I had the holes drilled, I began to install the female RCA plugs as shown in the picture


One important thing to keep in mind when you wire this, is MAKE ABSOLUTELY SURE THAT THE POSITIVE WIRE IS CONNECTED TO THE INSIDE CONTACT!!!

If you connect the positive wire (red or yellow, whichever color you use) to the OUTER contact, it’s in direct contact with your case, and you will shock your components. Just remember that the black wire gets connected to the outer contact and you should be fine.

Wired Up

Now that we have that finished, replacing the molex connector on the fan is easy. Just snip the wires and connect them to the male RCA connector (again, make sure the red wire is connected to the inside contact[the pin]).

Instead of soldering, I found that it’s much cleaner to use shrink wrap tubing for this. Just put a small diameter piece around the inner contact, and put a larger diameter piece around both contacts, then slide the shield back on and viola!


You now have an external fanbus for your system. As far as its connection to a PSU, I plan on connecting it to my internal fanbus, so I just left the leads bare. You can, if you saved the male molex connector, connect your external fanbus to that; just make sure you get the pins placed so that they’re connected to the BLACK and YELLOW wires from you PSU, and not the black and red wires.

For any of you who don’t already know, the yellow wires are the +12V line, and the red wires are the +5V line. And now you’re all set.

Dan Moeller

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