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How to Install Extra Fans in a PC Case (& Connecting to the Motherboard or PSU)

The Complete Beginner's Guide to Installing Aftermarket Case Fans (Airflow Basics)

So if you have an extra case fan or two (or 3, 4, or a gazillion) in this guide we will cover all the basics of where and how to install them in your case, how to position them the correct way, the basics of PC airflow, and how to connect case fans to either your motherboard or power supply.

1. Where to Install Fans in Case (PC Airflow 101)

Ideally you should have decided where to install extra case fans before buying them, but if you're still planning your fan setup, let's briefly go over how computer case airflow works in absolute basic terms. The role of computer fans is not to simply blow air onto your components to cool them. That's not how effective PC airflow works. Instead, most computer cases are designed in a way where air flows from the front to the back (and from the bottom to the top if your case has the option for bottom and top mounted fans).

The relatively cool air from outside of your case (the cooler the room where your PC will live, the better) is sucked/pulled in through the front of the case by one or more front fans (called intake fans). That cool air is pushed through the inside of the case, cooling your components in the process, and is then pushed/expelled out the back of the case by one or more rear fans (called exhaust fans).

How Many Fans Should a Gaming PC Have?

Exactly how many fans you need to install in your gaming PC and exactly where they should be placed depends on various factors, and there's no one size fits all answer. Computer airflow optimization can get a little complex though, and is beyond the scope of this article (will discuss in future on the site at some point though). But let's go over the absolute basics in a nutshell, and without getting too technical.

As a general rule, for most gaming PC builds you should have 2 fans minimum (1 rear and 1 front).

Remember this is talking strictly about case fans, and NOT including the fans included with the PSU, CPU, and graphics card. And make that 3 fans minimum for high-end builds with powerful gaming CPUs and GPUs. Anything more than 3 or 4 fans is likely to only give small, diminishing returns, and when you see people fully kit out a build with a boatload of fans it's usually for aesthetics and not practicality (but again, it completely depends, and so certain monster setups may benefit from a ton of fans).

For lowered-powered PCs such as a light gaming build using an APU like the Ryzen 3 3200G or Ryzen 5 3400G (integrated graphics, ie no graphics card), or for a basic home office PC, you wouldn't even need to add a front fan and could actually get away with just having a single exhaust fan. I mean, even more powerful gaming builds with a GPU could even be fine with just a single exhaust in the entire build, but I wouldn't personally recommend it.

What About Positive vs Negative vs Neutral Air Pressure?

As for balancing the number of intake vs exhaust fans to maximize airflow and/or reduce dust buildup, that's a more complex topic beyond the scope of this guide. But to summarize, there's no real clear-cut answer on whether a positive pressure fan setup (more intake fans than exhaust fans), negative pressure setup (more exhaust than intake), or neutral (same amount) is best and it all depends on the case (among other factors).

They all have their pros and cons, and it's a heated debate (pun intended) with different opinions on the matter, with a positive pressure airflow setup helping to avoid dust (to extend longevity of your system and make maintaining/cleaning easier) and negative pressure airflow setup generally helping airflow (but increasing dust).

A neutral pressure case is another viable option where you have an equal amount of intake vs exhaust fans. Also remember that when calculating the number of intake fans compared to exhaust fans, you need to take into account fan speeds too (which can alter the type of pressure in the case). But don't count the CPU, GPU or PSU fans in your calculations.

The general consensus in the DIY community is to setup a slightly positive pressure fan setup with say 2 intake fans and 1 exhaust (or 1 intake and 1 exhaust which is another common setup that works fine for many) because you'll get the benefits of less dust build-up and because there generally isn't much difference in temperatures between positive and negative airflow.

2. How to Know Which Way Case Fans Should Face

Before installing a fan, you want to figure out which side of the fan blows/pushes out air and which side pulls/sucks in air so that you install it the correct way around. Installing fans in the incorrect direction will mess up the airflow and lead to potential overheating or damaging of your parts.

For example, if you want to install a fan in the front of your case to act as an intake fan (to suck air in from outside and flow it through the inside of your case), if you position it the wrong way around then instead of pulling air in from the front it will be pulling air in from inside the case (and expelling it out the front). Not good.

But the question is, how do you actually know which side of the fan blows the air out?

It's not immediately obvious if you're doing this for the first time, but some case fans will have an arrow printed on the outside of the actual fan (on the top or the side) to indicate which direction the air will blow. When mounting front intake fans, you want the arrow pointing into the case, and for mounting rear exhaust fans the arrow should point outside the case. Some will have two arrows to indicate both the direction of the air as well as the direction that the fan physically spins.

Some fans won't have any arrow though, in which case you can figure out the direction by either noticing which side the spokes/grille is on (the bits that hold the fan motor to the frame), or by looking at which side the brand sticker is on (the label on the middle of the fan). The side of the fan with the sticker and the spokes is almost always the side where air will blow out. So for installing a front fan for example, the spokes/sticker should be facing inwards into the case. 

Confirming Your Fans Are Installed Properly

If you want to absolutely make sure you've installed fans the proper direction, when you turn on your PC hold a tissue or other very light material in front of each fan to test it. If you see the tissue being slightly pulled towards the fan, that side is the intake (pull). If the issue blows outwards a bit, that's the exhaust side (push). For example, if you hold a tissue outside the case just in front of a front intake fan, the tissue should move slightly towards the fan.

3. How to Remove Front Panel of PC Case

For our example build using the DeepCool Matrexx 30 case, you pull from the bottom of the panel to remove it. It doesn't matter if your case is sitting upright or lying on its side when pulling off the front panel - just position it whichever way is easiest for you to get a good, controlled grip:

4. How to Mount and Screw Fans Into PC Case

In most cases, you'll have the freedom to install front fans at different heights. If you're just installing one front intake fan, you're probably best off installing it at the bottom as pictured below, though in certain setups it might be better to position it in the middle of the front so that it directly blows air onto the motherboard area. If in doubt, just install it in the front bottom:

You also want to position the fan so that the cable (that will plug into the motherboard or PSU in the next step) has the easiest access to the inside of the case. Otherwise, the fan cable might not be able to reach all the way to the motherboard. Just keep in mind that if the fan cable doesn't reach the motherboard no matter which way you install the fan, don't worry as you can either buy a fan cable extender (3 or 4 pin depending on your fan) or you can use a molex adapter (which may have come with your fan) to connect the fan to the PSU instead. We'll cover this in a bit, but let's finish mounting the fan.

Screwing the fan in might require a fair bit of force if the fan holes are unthreaded, which is usually the case with plastic fans (Acrylic fans are typically pre-tapped/threaded already as Acrylic cracks more easily). So when screwing in the mounting holes for the first time, you're going to need a decent amount of force to thread the holes for the first time (and then in future it'll be easier to screw in should you ever need to remove and re-install the fan).

In terms of how tight to screw the fan in, you want the fan nice and tightly mounted to avoid vibration/rattling noises, but as with installing any other PC components, you don't want to go crazy and over-tighten the screws so much that it would make uninstalling them later a job fit only for a Greek god like Zeus. Tight, but not too tight.

5. How to Connect Fans to a Motherboard or PSU

Now you've installed the fan/s, all that's left is to plug them into your system. If you're installing these fans as part of a full new PC build, you obviously can't plug them in just yet until you've finished installing all your PC components (specifically, until the motherboard is in your case). But if you're here mounting extra case fans as an upgrade to an existing PC, go ahead and plug them in now.

Case fans can be connected to your PC in 2 main ways:

What if Your Motherboard Doesn't Have Enough Fan Headers?

Connecting Fans to a Power Supply

If you plug case fans directly into the PSU (Power Supply Unit), you won't be able to control the fan speed and the fan will always run at full speed. Sometimes you have to plug a fan into the PSU though (if your motherboard perhaps doesn't have enough fan headers for all your fans), but it's not really a problem unless you really wanted to control fan speeds.

To plug a case fan into the PSU, your PSU you will need to have 4 pin molex connectors (not all PSUs have these, but many will). You'll also need a 3 pin to molex adapter (some fans come with this), which you plug into the fan to be able to then plug into the PSU's molex cable.

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