My 5V fan mod with kitchen shears: ok to do?

Massachusetts · Post by **Massachusetts** » Wed Oct 07, 2009 8:08 am

Hi SPCR's. As part of my quest for an awesome home theater setup, I'm trying to re-engineer my cooling solution to get quieter operation. Naturally I've made this site a basis of my research. While building the system, I thought of a simple way to get 5V out of molex-connected fans, but I couldn't find it on the internet so I got worried and thought I'm missing something obvious.

I have some Yate Loon 120mm fans which are acceptably quiet at 5V but horrible at 12V. I've read the SPCR guide to adding a switch to my case fans. I have no desire to ever use 12V mode, however, so I thought I'd rather do it an easier way. This way mods a 4 pin molex fan to take 5V instead of 12V using kitchen shears.

This is the molex plug on the fan. As you can see molex connectors are polarized with two divots on the top so they only fit one way. The idea of the mod is to modify the plug so that the molex header from the PSU can be inserted upside down into the female fan plug. This will cause the fan to be powered from the red 5V line instead of the yellow 12V line.

According to SPCR the wires on a standard molex connector are 12V (yellow) / ground (black) / ground (black) / 5V (red).

A tiny snip on the angled part of each side of the fan's plug should allow it accommodate the square-edged side of the molex plug on the PSU instead of the angled side.

Yep. It fits snugly too. Left side is from PSU, right side is fan plug. Notice that the two wires trailing down from the fan side are connected to the Red/Black pins from the PSU. This is the 5V line going to the fan. This fan plug has a molex extender on it, WHICH IS NOW REVERSED. The yellow line on this extended plug is the 5V line and mutatis mutandis the red. This is great if you want to set up two 5V fans in parallel as I did; you don't need to snip the second fan. However it could be dangerous if you forget and use the extended molex for something that needs 12V. So don't do that.

Two 5V yate loons in series. Virtually inaudible.

Whaddya think, is this way good or not?

Edit: Yeah, parallel. Not series. Thanks.

Post by **NeilBlanchard** » Wed Oct 07, 2009 8:33 am

Hi,

Congratulations on coming up with a very workable and nearly free voltage mod!

swivelguy2 · Post by **swivelguy2** » Wed Oct 07, 2009 9:50 am

Clever mod. One small point though - I think your fans are in parallel at 5v, not in series. Series would give them 2.5v each, and they probably wouldn't start.

Mr Evil · Post by **Mr Evil** » Wed Oct 07, 2009 12:58 pm

My preferred method is to move the pins around on the connector. If you look closely, you will see two thin strips along each pin, splayed out to prevent it from being pulled back though the shell. Simply push them in with a small screwdriver and the pins come out. You can then rearrange the pins in any way. It takes about 30 seconds to do, and it's completely reversible.

Massachusetts · Post by **Massachusetts** » Wed Oct 07, 2009 1:00 pm

Mr Evil:

That sounds like a good way, but personally I will prefer the safety of having the voltage switch on the unpowered side to the ability to reverse the mod.

ntavlas · Post by **ntavlas** » Wed Oct 07, 2009 1:12 pm

I used to rearrange the pins on the molex too but trimming the edges of the plug is much more practical.

It`s a good thing someone shared this useful information.

Mr Evil · Post by **Mr Evil** » Wed Oct 07, 2009 1:41 pm

Massachusetts wrote:Mr Evil:

That sounds like a good way, but personally I will prefer the safety of having the voltage switch on the unpowered side to the ability to reverse the mod.

It's the unpowered side I'm talking about: pins = male, sockets = female.

wwenze · Post by **wwenze** » Sat Oct 10, 2009 5:20 pm

Best part of trick - ability to switch between 12V and 5V without removing the pins (again) or through a 12-5V-swap adapter cable.

That's a great trick that nobody's mentioned till now.

However it could be dangerous if you forget and use the extended molex for something that needs 12V.

For my 12-5V adapter with daisy-chain capability I pasted a sticker and wrote a big "5V" on it.

frostedflakes · Post by **frostedflakes** » Tue Oct 13, 2009 12:01 am

ntavlas wrote:I used to rearrange the pins on the molex too but trimming the edges of the plug is much more practical.

It`s a good thing someone shared this useful information.

Switching the pins is how I do it as well. I didn't even think about trimming the connector like that, though. Pretty clever, I'll have to try that out some time.

Parappaman · Post by **Parappaman** » Sun Oct 18, 2009 3:16 pm

Rearranging pins is waaaaaaaaay much more professional (and undoable) than this, but hey, everyone should create his mods the way he likes them more, so if you like this, then it's a good one