Easy 5v fan power hack

[matt_garman]

Armed with the knowledge from Mike Chin's excellent article Get 12V, 7V or 5V for your Fans, I sought an easy way to run my case fans at 5v.

I bought one of those 3-pin ATX fan to 4-pin Molex adapters. I realized that the two wires from the 3-pin fan connector are attached to pins one and two of the 4-pin Molex connector. According to Mike's article, Molex pins one and two correspond to 12V and ground (respectively).

So I just swapped pin one with pin four on the molex connector, and likewise for pins two and three. Now the two leads for the 3-pin fan connector are wired in parallel to pins thee and four of the molex connector (aka the 5v and ground leads, respectively).

It's pretty easy to move the pins of the molex connector. Note that this operation took place on the male end of the molex connector. The pins are essentially straight poles that flare out to keep from slipping through the plastic. If you look down on the poles, you should be able to see two flanges that stick out a bit (holding the poles in place).

You can take a small flathead screwdriver and push those flanges in to be flush with the rest of the pole. Then the lead will slide right out of the plastic. Once the lead is out of the plastic, you can gently flare the flanges out a bit, so that when the pole is pushed back through the plastic hole (in its new location), it will "snap" into place.

This is fairly hard to describe in words; I don't have a camera or I'd take some pictures to explain the process.

I hope someone finds this suggestion useful.

Matt

[HammerSandwich]

So I just swapped pin one with pin four on the molex connector, and likewise for pins two and three.

The ground wires connect to the same place, so you don't need to swap 2 and 3. This is a convenient mod and also the way I handle 5Ving, but be sure you don't ever plug the 4-pin extension into anything that needs normal power (e.g. hard drive).

[JimK]

HammerSandwich is right.

Swap wires on the female plug too. Or cut out the other pair of wires so only the 5V pair remain. Right now you have a connector that looks OK but puts 12v on the 5v side. Two years from now you will pick this thing up and use it to connect your new 500GB 15dB harddrive and melt some of the little things inside. Or worse your old 160GB drive with all that data on it. Others here have done it.

[al bundy]

You can also label the molex connectors with a permanent black sharpie pen or something, indicating the voltage they provide (like this guy did for example)...

[SebRad]

Hi, in a similar vain, the other day I discovered that you can take the pins out of a 3 fan header plug. I left the sense (rpm monitoring) wire in the plug and plugged it in to the fan header on the board. I then pushed the bear metal ends that I'd taken out, of the 3 pin plug, in to a molex connector (+ve to 5V[red] and -ve to earth[black]), it's a nice tight fit with no modifying needed. This gave me a fan running at 5V with rpm monitoring at no cost and completely undoable. This trick doesn’t work on "7V mods" probably as the earth is connected to the 5V not ground. The colour schemes I've seen are:
-------------Positive----Negative---Sense
Normal-----Red--------Black-------Yellow
Intel--------Yellow-----Black-------Green
Hopefully useful to someone,
Seb

[chylld]

You could also just take some a scissor/knife edge and angle out the unangled corners of the molex plug so that it plugs into the psu connector the other way around