Did you know that you can modify any fan located inside your PC – CPU fan, VGA fan, north bridge fan, case fan, etc – to run at three different speed levels (low, medium and high) without spending any money at all? This is possible by just changing the configuration of the wires used by the fan. In this tutorial we will give you detailed instructions on how to do that, reducing the noise produced by your PC.  

Fans can have two, three or four wires. Below you have a breakdown of the function of each pin and the most common color for the wire attached to that pin. There are two important things to notice here. First the color of the wires may change depending on the fan manufacturer. These are just the most common ones. Second, all fans are fed with+12 V; however several fans use a red wire on their +12 V line, being different from the color code used by the power supply, where red means +5 V.

Also notice that during this tutorial our examples will be with a CPU fan, but everything we say is valid for any kind of fan located inside the PC: video card fan, chipset fan, case fan, etc.

On Figures 1 and 2 you can see a three- and a four-pin connector, respectively. Notice that the counting is done with the key present on the connector up.

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Figure 1: Connector from a CPU fan using three pins.

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Figure 2: Connector from a CPU fan using four pins.

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Figure 3: CPU fan connector on a motherboard. You can install either three- or four-pin fan connectors here.

The first two pins supply the voltage required for the fan to spin. The third pin is connected to the fan speed sensor, reporting to the motherboard the current fan speed. This value can be read at the motherboard setup (see Figure 4) or thru a monitoring program, such as Motherboard Monitor. And finally the fourth pin is a speed control input, also known as PWM (Pulse Width Modulation) control, provided by the motherboard. On fans that have this fourth pin the motherboard (or video card) can control the speed of the fan, usually automatically depending on the CPU or GPU (graphics chip) load.

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Figure 4: Motherboard setup.

If your fan has four wires, you don’t need to do what we will teach in this tutorial, as you fan has already a speed control circuit. Just go to the motherboard setup and look an option to enable this feature (“CPU Smart FAN Control” and setting mode to “Auto” on Figure 4). This will reduce the CPU fan speed automatically when your computer is idle or when you are not using a heavy application like playing a game.

If, however, you are not satisfied with the PWM control provided by your computer, you can remove the fourth pin (see how on Figures 6 and 7) and execute the procedures described on this tutorial.

Reducing the fan speed is just a matter of feeding it with a lower voltage. But how can we do that if the fan connector only provides +12 V? That is exactly the trick we will teach you: we will remove the fan power wires from the fan connector and install them directly to one of the peripheral power plugs from the power supply. This way we will be able to feed the fan with +5 V (low speed), +7 V (medium speed) and + 12 V (full speed). Read on.