Easy 7V Mod for Fans

Author: tski
Date: 2006-04-11 18:36:00


Today I’m going to show you how to do a simple mod that you can use to quiet down your fans. This will allow you to use any 12 Volt fan at 5 Volts or 7 Volts.

Tools Needed

The tools needed for this job are a small jeweler’s type screwdriver (standard “flat-head”) and a set of wire cutters. To make the job easier, you can use a Molex-pin removal tool, but it is not necessary. I will also be using a multimeter today to show you the Voltages.

To make the adaptor you will need either a dead or cheap 4-pin fan, or a 4-pin to 3-pin adaptor that has four wires between the male and female Molex plugs. The fan I will be using is a Thermaltake Thunderblade fan that I plan to convert to 3-pin.

Step One

Here is a picture of what we need. Our first step is to remove the fan wires from the pass-through connection. Insert your Molex-pin remover and pop out the pins one at a time. If you don’t have the removal tool and you are using a small screwdriver instead, simply slide the screwdriver along the side of the pin and push in the two small clips that hold it in place (you will see an example of these clips in a moment).

Step Two

Now that you have removed the pins you can use your wire cutters to snip off the extra wire from the fan (or 3-pin adaptor).

Step Three

Before inserting the wires back into the Molex connector, make sure to take a good look at the clips on the pins. They will be pushed into the pin, and chances are the removal tool might have bent them. You need to use your small screwdriver to gently pry the clip out of the pin and flatten it out if necessary. The third pic below shows the clips fully extended.

Step Four

Now that we have the extra wires removed from the pass-through connection, we can remove the other two wires: the 5 Volt (red) and the ground wire for the 5 Volt (black). Use your removal tool or screwdriver and repeat the steps above.

I will show you the different options available. First, if we leave the wires as they are in the Molex connection, we get 12 Volts. Now, in reality you wouldn’t want to do that, as it would just mean extra wires. However, this helps to show you that the yellow wire is the 12v, and the black wire next to it is ground.

5 Volt Mod

To get different Voltages, we will be moving the wires around. This needs to be done on the side of the connector that the power supply goes into. For 5 Volts, you would need to take the pin for the yellow wire and move it to the red wire. The black wire for the ground doesn’t really have to be moved. Both ground wires are truly shared by the power supply.

7 Volt Mod

There is a good possibility that your fan will run at 5 Volts, but it may not start at 5 Volts. However, most fans will start at 7 Volts and still not be as loud as when running at 12 Volts. To get 7 Volts, you will need to leave the yellow wire in its original place, and move the ground wire to the red 5V location. Yes, you read correctly. It sounds weird, but what this does is kind of like subtracting the 5V from the 12V. If you noticed the Voltages in the pictures above:


This is why the Voltage shown below is slightly less than 7V. (There is fluctuation in the Voltages, so that is why the math doesn’t add up with the Voltages in the pictures.)

Now if you have 3-pin fans to connect, you can use a 4-pin to 3-pin adaptor and daisy-chain as many as you would need. If that is too bulky for you, you can always cut off the 3-pin wires, group all the red wires together and connect them directly to the yellow wire with a crimp connector or solder and heatshrink tubing. Then, group all the black wires together and connect them directly to the black wire the same way.

There you have it: a quick easy mod that lets you run your fans at 5 or 7 Volts. Total project time should be around 5 to 10 minutes. Just please remember to only hook up fans or lighting to this mod, as drives or other peripherals may be damaged by the improper Voltage connection.

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