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Which way around does a CPU fan go?


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#16 papercut2008uk

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Posted 04 September 2013 - 17:46

sounds like your going to be replacing the fan soon, if it vibrates or rattles when upside down or orientated differently, the bearings have warn a lot, so you'll probably start getting vibrations or buzzing.

 

i've noticed that when you clean out a CPU fan that has been dirty for a while, this does happen, it wares the bearings out faster and when you clean the fan it starts to make a noise.




#17 Sir Topham Hatt

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Posted 06 September 2013 - 10:13

I always thought fans should be pushing air away from the components.

However I noticed yesterday as I was mounting case fans that the CPU fan is drawing air towards it.  Is that really right?  Should case fans be pushing air out the case or drawing it in?



#18 Aheer.R.S.

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Posted 06 September 2013 - 10:18

In mine, I have 5 blowing into the case, 1 extracting (the one on the psu)

Then there's the ones on my graphics cards, they blow into the cards, and the one on the heatsink, again blowing into the heatsink



#19 Andre S.

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Posted 06 September 2013 - 16:30

I always thought fans should be pushing air away from the components.

However I noticed yesterday as I was mounting case fans that the CPU fan is drawing air towards it.  Is that really right?  Should case fans be pushing air out the case or drawing it in?

Fans mounted on components like the CPU and GPU fans always blow air towards the component as this is much more efficient at cooling it. If you need to convince yourself of this, just try standing behind a fan rather than in front on a hot summer day. Case fans, however, typically alternate between intake and outtake to create a clear airflow path through the case.



#20 OP moeburn

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Posted 06 September 2013 - 16:37

Since we're still on the topic of fans, maybe someone can help me out with this question:

I'm trying to install a 3rd fan on my 3rd PWM controller, but I can't find the 3-pin plug on my motherboard.  Could it be that even though Speedfan and OpenHardwareMonitor and lm-sensors and pwmconfig all find a third PWM controller, there is no connector on the motherboard?  I did see plenty of other solder holes with no components soldered to them, perhaps the third 3-pin pwm controller is wired/traced on the motherboard, but the jack was never soldered to it?



#21 Aheer.R.S.

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Posted 06 September 2013 - 16:38

Could be, but it's not hard to re wire a molex into it

I had to as although my case supported 6 fans, my mobo didn't



#22 Andre S.

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Posted 06 September 2013 - 16:39

Not every motherboard has that many fan controllers. In that case you'll have to use a molex-to-3pin adapter.



#23 OP moeburn

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Posted 06 September 2013 - 16:41

Not every motherboard has that many fan controllers. In that case you'll have to use a molex-to-3pin adapter.

 

But that means I won't be able to PWM control it from the operating system, right?  The only spare fans I have are noisy at full speed.  I did successfully wire a potentiometer to one, but it meant bending over to the computer case every time I wanted to change the fan speed.  Also the pot got pretty warm absorbing all that current.

 

Hmm... my CrystalFontz CFA-633 LCD screen has some 3-pin fan connectors on the back of it, maybe I should see what those are for...



#24 Andre S.

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Posted 06 September 2013 - 17:18

But that means I won't be able to PWM control it from the operating system, right?  

Yup, that sucks. My HTPC is really noisy precisely because of this, and I've been too lazy to bother trying to find a solution. Let me know what you end up doing.



#25 tsupersonic

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Posted 07 September 2013 - 13:52

Yup, that sucks. My HTPC is really noisy precisely because of this, and I've been too lazy to bother trying to find a solution. Let me know what you end up doing.

I don't know how much space you have in your HTPC case, but a fan controller might work.

#26 OP moeburn

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Posted 07 September 2013 - 15:34

I don't know how much space you have in your HTPC case, but a fan controller might work.

 

Or you could do it the moeburn way, and try and make your own PWM controller out of a simple 555 timer!

schematic-pwm-controller-eagle.png

 

http://3lectronics.c...ulator-diy-555/

 

That one is a broad-range controller for anything that runs on 12v, but is specifically stated to work as a fan controller.  And the author has even included how to lay it out and solder it on a standard breadboard!  You'll need a fancy MOSFET (Q1) though, which isn't always something people have lying around in their electronics bins like a 555 timer.  :)



#27 Sir Topham Hatt

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Posted 08 September 2013 - 07:27

If you need to convince yourself of this, just try standing behind a fan rather than in front on a hot summer day.

This sir is a very good point well made.