Your computer is a hot mess. It has several hardworking, electrical components that generate a lot of heat. If you noticed, the two main hardware components have their own dedicated fans: your CPU (or Central Processing Unit) and your GPU (or Graphics Processing Unit).

These powerhouses are creating visually stunning worlds and lush environments so, of course, they’re going to run your computer hot. And that is where you PC fan comes into play.

Deciding on a Computer Fan

Deciding on a PC fan has several moving parts. They can be broken down into three components: What can your case support? The fan size and the brand. Fan support and the PC fan itself are, of course, the most important aspects. The company you buy from is easier to work with.

I Don’t Know My Fan Size

Don’t panic. You have two choices: have someone else tell you or you can measure the fan yourself. Before you go measuring, you should know that a PC fan is not measured like a TV or computer monitor would be (from corner to the opposite corner). A PC fan, like a 120 mm fan, is 120 mm on every side. Don’t measure one screw to the next; that will give you an inaccurate measure. Measure from one edge to the next, and not the fan itself, either.

If you choose to have someone tell you the measurements, you’ll need to remove the fan from the PC. In order to do that, you’ll need to follow the steps provided under “Removing the Computer Fans.”

Choosing the Fan Size

What you need to do first, before deciding on a fan, is examining your case. This is going to give you the best possible idea on where to start, regarding the size of the fan you’ll need.

If you bought a computer recently, or in the past couple years, chances are your case can support a fan as big as 120 mm. However, obviously, that isn’t the case for everyone. If your case only supports an 80 mm PC fan, don’t get a 120 mm fan; it will be wasted and inefficient.

Fans come in various sizes, but the three most popular ones, the PC fans you see the most, are: 60 mm, 80 mm and 120 mm. Most modern computers support and come with 120 mm as their stock option. As it was mentioned, you usually want to go for the biggest fan you can support.

With, say, a 120 mm fan, every revolution it makes (the time it takes for one blade of the fan to make a complete circle) is going to blow out more fan; it doesn’t have to work as hard to push air out. This is going to work in your favor, especially considering a computer can get very hot if it isn’t regulated right. Far more quiet, far more efficient.

Choose the Correct Power Connector

It will make you pull your hair out if you pick the fan you want, wait a few days to get it and when you do, it doesn’t have the connector you need. You’ll start a riot and it’ll be on the news and everyone will know what you did. Probably.

To avoid possible rioting, examine the power cables your motherboard comes equipped with. What you’re looking for are chords known as “molex.” Molex cables have a white, plastic-looking end on them and the most common are 3-pin and 4-pin. Chances are you’re dealing with either one, but if you don’t know for sure, you can always have a friend help or search for it with a search engine and compare.

For those wishing to control the speed of their fan, you’ll want to connect the PC fan to a supported connector located on your motherboard. There does exist a few programs that can change the speed without the motherboard, but that’s pretty hit or miss. It isn’t necessary, but it is better to have that connection and not need it, than to need it and not have it.

Be Mindful of Air Flow

As air moves naturally through your computer case, your case fans suck that air out, thus, keeping any of that air from hanging around and getting hot. It’s why computers have so many small holes and a dedicated case fan; hot air needs a place to go. That air flow is measured by CFM, or “Cubic Feet per Minute.” A good rule of thumb to keep in mind is case fans work best when they have a much higher CFM.

Choosing a Brand

The question, “Which brand should I choose?” is a pretty loaded question. You want quality above all else and, if your budget allows for it, maybe some LED lights for a bit of pizzazz.

There’s dozens of PC fan manufacturers to choose from, but the companies listed below are a great place to start.

For a lower budget, choose a fan without LED. All it does is add flair and, quite frankly, that’s useless. It looks great in a PC, but it does nothing for your PC.

Installing the Computer Fans

Preparing the Workspace

1. First things first: shut your computer down completely. Give your computer at least 120 seconds to completely shut down all processes.

2. In the back, near the power cable, flip the power switch.

3. Remove the power cable from the electrical outlet.

4. Press the power button and hold your finger there. Hold it for 15 seconds to ensure that all power left behind has been discharged.

5. This step is very important. If you’re computer is in a location with carpeted flooring, immediately move it somewhere else, preferably a table, like a wooden table. Carpet, if you didn’t know, has a knack for creating static electricity. Computers and random electrostatic discharge from your fingers and body do not play nice with each other. In fact, you can seriously damage your computer.

Even better, buy yourself an electrostatic wrist strap to ground yourself. Touching metal objects can also remove any static. Be ever vigilant against the tyranny of electrostatic discharge.

6. Now you’re free to remove the panel from your computer. This can vary from case to case because side panels come in different shapes, sizes and ways of opening and closing. For example, some cases have thumb screens.

You may have a side panel that’s on a hinge, which most can be removed by opening the side panel and lifting the side panel up. Other side panels have flipback latches and other forms of latches. Identify and remove accordingly.

7. If you’re installing more than one fan, know that most cases are equipped with support for more than one fan. You’ll notice vents and, chances are, a fan can go there. For example, you may find a vent on the top, on the front, even on the side panel, but most importantly, there’s always one in the back.

8. With your computer wide open now, you’ll want to find the power connectors. These are going to be absolutely needed when you install the fan. Check your motherboard for fan connectors labeled “CHA_FAN#” and “SYS_FAN#.” Those two are pretty common.

Install the PC Fan

Now that you’ve identified your power connectors, you’re standing on flooring that won’t make you a conductor of electrostatic and you have the pc fan in your hand–you’re ready to install the fan.

1. Follow the cable to your old PC fan and find where it’s connected. Remember that place if you plan on connecting your new PC fan to it. Unplug the power connector.

2. Unscrew the computer fan from your case. You can find the screws on the outside of the case. And hold onto the computer fan while you unscrew it so you don’t incur damage when it falls. You don’t need to buy a new GPU, too.

3. Remove the PC fan and replace it with your new PC fan, but be mindful of you’re placing it. The PC fan only blows air in one direction. A PC fan in the back needs to blow air out. Check out the stickers placed on at the center of the fan. The side that has a sticker is the side you want facing away from your computer components, not towards.

4. Start with screwing in your fan. With one hand, hold the PC fan in place and, at the same time, secure it to your case with screws. Remember, righty-tighty, lefty-loosey. Be careful you don’t stripped the grooves.

5. Once the computer fan has been screwed in, you can go ahead and plug in the power connectors.

6. Power your computer back on.

From here on out, you can use your computer normally. However, you can use your BIOS to check the speed of your fans if they were connected to the motherboard.

Without the extra fans, your computer would overheat and, eventually, destroy itself. By having a rear fan, and a few extra if you want them, your computer can take that generated heat and suck it right out because it isn’t enough that your CPU and GPU have their own fans; that heat has to go somewhere.