# Fan Flow Direction



## ShosMeister

Here's a real newbie question for you guys. Most of the fans I've noticed do not show the direction of air flow. I'm guessing it's assumed that everyone who is building a case knows which direction is which, but, for us new guys, how do you know? Is it a trial and error; just plug it in and see with way is spins?


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## Computer_Doctor

Usually the fans in the front pull in air while on the contrary, the fans hooked on the back of the computer pull air out.


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## ShosMeister

Sorry for not being clearer Doc. That much I know, but, if I'm installing fans, how do I know which way to install them?


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## 2pistolpacker

On the sides of most fans, there are arrows which point to the direction of airflow and fan rotation. Mike


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## ShosMeister

I was thinking that as well, but, most of the fans I've been looking at, I can't see them and the only ones I have around the house are very old.

Thanks!!!!


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## 2pistolpacker

On all the fans I have, there is a brand sticker on the front frame. As you are reading the sticker the air flow would be blowing in your face. Mike


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## emosun

I see what hes saying , heres an easy way of telling. The air goes in through the side that has just the fan rotor and comes out the back where the motor attaches to the rest of the fan frame. As 2pistolpacker said , the side with the sticker is where the air comes out. Remember that the fans only turn in one direction and that reversing the wires won't make them spin in the opposite direction.


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## ShosMeister

Awesome. Thanks guys! I guess I WAS thinking that it could be reversed by reversing the connector. Can you tell this is my first attempt to build a machine?  

Thanks!!!!


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## ShosMeister

One other question. What's the major reason some fans have 3 pins and others have 4? If I were going to add a fan to a case, should I get a 3 or 4 IF I was planning on having a fan controller? I've noticed a lot of the controllers only handle 3 pin fans (maybe 1 4 pin fan) so, is there a reason to get a 4 pin?


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## Rob 1

ShosMeister said:


> One other question. What's the major reason some fans have 3 pins and others have 4? If I were going to add a fan to a case, should I get a 3 or 4 IF I was planning on having a fan controller? I've noticed a lot of the controllers only handle 3 pin fans (maybe 1 4 pin fan) so, is there a reason to get a 4 pin?


Mainly it comes down to there not being a single standard for fans.

I use Antec Tri-Cool fans on all my cases. They have a small attached 
3-way switch. Almost all of the fans that I run are 120mm, so I can run them at whisper quiet low settings and still get good cooling.

As far as the direction goes, if you have a fan location in front of your hard drives, you of course want the fans blowing towards the hard drive, and not the opposite.

Simplest way to check fan direction is to just plug it in and see which way the air flow is.


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## ShosMeister

Thanks Rob. I was looking at 120mm fans as well. The question though is the number of pins on the power cable (3 vs 4). Differences? Why? Are 3 pin fans okay if I want to get a fan controller that only has 3 pin connections?


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## ShosMeister

Wait a minute! I started looking again on NewEgg and noticed the 4-pin fans have power connectors like IDE hard drives. What's with that? Is that what they ALL mean when they indicate 4 pin connectors? I was thinking it was similar to the 4 pin CPU fan connector, maybe not? If all of the case fans with 3 or 3/4 pin connectors will work just fine on a bay fan controller, then I guess I don't have an issue other than making sure I don't exceed the power draw of each fan.

Am I right or am I missing something else? Thanks!!!


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## Rob 1

ShosMeister said:


> Wait a minute! I started looking again on NewEgg and noticed the 4-pin fans have power connectors like IDE hard drives. What's with that? Is that what they ALL mean when they indicate 4 pin connectors? I was thinking it was similar to the 4 pin CPU fan connector, maybe not? If all of the case fans with 3 or 3/4 pin connectors will work just fine on a bay fan controller, then I guess I don't have an issue other than making sure I don't exceed the power draw of each fan.
> 
> Am I right or am I missing something else? Thanks!!!


I think you're mostly wondering about being able to control the fans?
The 3-pin fans allow for that. Those are the small square connectors that plug into the motherboard, and can be controlled by software like speedfan, or in the motherboard's bios.

And the 4-pin versions are like you said. They are the molex connectors that you connect hard drives to.

Those won't give you motherboard control.

Then there are proprietary types of fans that come with a seperate fan control that can fit into an optical bay, like what you were talking about.
Those can be literally whatever the manufacturer wants to use, but wil typically get their power feed from a 4-pin molex connector.
From there, they will connect to the controller with whatever plug the manufacturer chooses to use.


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## ShosMeister

Awesome explanation Rob. Thanks!!! I think I'm good with the case, fans and controller that I'm thinking about. May need to get an extension CPU Fan cable as the controller has a spot for that as well, but, that should be easy to find.


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