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Home » Cooling
How to Create a Three-Speed Fan Control without Spending a Dime
Author: Gabriel Torres 400,653 views
Type: Tutorials Last Updated: November 15, 2007
Page: 1 of 3
Introduction

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, thus 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 the most common ones. Second, all fans are fed with +12 V; however, several fans use a red wire on their +12 V line, which is different from the color code used by the power supply, where red means +5 V.

Pin

Function

Wire Color

1

Ground

Black

2

+12 V

Red or Yellow

3

Fan Speed Sensor

Yellow, White or Green

4

PWM Control

Blue

Also notice that during this tutorial, our examples will use 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.

In 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 facing up.

How To Reduce Fan Speed
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Figure 1: Connector from a CPU fan using three pins

How To Reduce Fan Speed
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Figure 2: Connector from a CPU fan using four pins

How To Reduce Fan Speed
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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 the current fan speed to the motherboard. This value can be read at the motherboard setup (see Figure 4) or through a monitoring program, such as Motherboard Monitor. Finally, the fourth pin is a speed control input, also known as a 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.

How To Reduce Fan Speed
click to enlarge
Figure 4: Motherboard setup

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

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

Reducing the fan speed is 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). Please read on.

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