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moeburn

Which way around does a CPU fan go?

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Just detached my cpu fan from my cpu heatsink for the first time, to get at the really bad gunk in between.  Reattached them, but I think I might have it the wrong way around, because it sounds way different now.

 

One side is very dirty, and one side is very clean.  The very dirty side has the label on it.  Which way should be pointing at the CPU, the dirty side or the clean side?

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alot of times it doesnt matter which way the fan goes, but just put it to blow air towards the heatsink if you're not sure. to tell which direction the air blows, look at the fan, there should be two arrows,one showing the direction of airflow, and another  one showing the rotation direction.

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Hold it in your hand then briefly power the machine on, if I ever mount a fan the wrong way around that usually helps me correct the issue pretty quickly.

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One side is very dirty, and one side is very clean.  The very dirty side has the label on it.  Which way should be pointing at the CPU, the dirty side or the clean side?

Why not CLEAN the fan ?

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Just detached my cpu fan from my cpu heatsink for the first time, to get at the really bad gunk in between.  Reattached them, but I think I might have it the wrong way around, because it sounds way different now.

 

One side is very dirty, and one side is very clean.  The very dirty side has the label on it.  Which way should be pointing at the CPU, the dirty side or the clean side?

Typically they have small arrows somewhere on the casing telling which way the air goes.  It should go outward to not push heat towards sensitive components.

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Why not CLEAN the fan ?

 

I tried.  It's that weird beige residue that dust leaves behind.  Like crude oil or something. It doesn't come off from vacuuming or wiping, and barely comes off with scraping.  It's not thick or anything, it's probably not adding so much weight that it slows the fan down.  

 

Thanks everyone!  I had it blowing air AWAY from the cpu accidentally.  Put it back to blow air towards the CPU, and it no longer sounds like a squealing monkey.  Yay!  

 

For anyone curious, the temperatures were about 5-8 degrees hotter blowing air away from the cpu, than they are blowing air towards the cpu.

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Thanks everyone!  I had it blowing air AWAY from the cpu accidentally.  Put it back to blow air towards the CPU, and it no longer sounds like a squealing monkey.  Yay!  

 

For anyone curious, the temperatures were about 5-8 degrees hotter blowing air away from the cpu, than they are blowing air towards the cpu.

 

You risk running out of air by doing that. Check atmospheric pressure.

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The reason it sounded like a squealing monkey, as you elegantly put it, is that it was so inefficient in that position that it had to spin at full speed constantly. A CPU fan usually spins relatively slowly which is what keeps it quiet.

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the thick gunk is from either someone smoking or incense/oils.

 

if you remove the CPU fan and heatsink, you need to reapply thermal paste, first removing the old stuff.

 

if you just remove the fan, the air should push into the heatsink, and ideally the fan should blow towards the back of the case if you have an exhaust fan or to the top if you PSU is the only exaust fan in the case, if you have an AMD CPU they usually only point either up or down, if it's an AMD heatsink you should position it with the exaust going up.

 

either have the fan side pointing towards the front of the case or the bottom of the case.

 

if it's just a stock fan it doesn't matter which way round it go's.

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In America/Europe, clockwise, but in Australia it goes counter clockwise :)

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If you get a pack of kitchen cleansing wipes (I usually use the dettol ones) those clean fan blades very effectively

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on the fan itself, label side up, (there might be a direction of airflow arrow on one of the sides, I usually set the fan to blow into the heatsink)

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I'm really hoping the "thick gunk" he's talking about isn't the thermal paste...

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Actually, I've seen some that have the label on the wrong side. The side with the little wires are the outflow way.

 

papst_silent_case_fan.jpg

 

That way is outflow.

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I'm really hoping the "thick gunk" he's talking about isn't the thermal paste...

 

I really hope you didn't put thermal paste between your fan and your heatsink...

 

I've taken off heatsink/fan combos and reapplied thermal paste on CPUs over a dozen times.  I know how to do that.  What I've never done before, is separate a fan from its heatsink.

 

The black gunk was the same stuff that had accumulated in the air filter on the front of the case (this case and cpu/fan were second hand from someone else).  They weren't a smoker.  It looks like crude oil, so thats what I call it.  They were Italian, however.  It may have been a combination of lots of dust, and the cooking oil fumes that permeated their entire house.

 

Didn't help that my fan actually had different labels on both sides.

 

The strange noise the fan was making when it was upside down was not the fan RPM increasing.  I use speedfan, and I checked when I heard the strange noise, and it was similar speeds.  It just didn't like being upside down, or maybe I didn't tighten the screws enough and it was slightly vibrating, or something.

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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.

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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?

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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

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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.

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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?

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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

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

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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...

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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.

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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.

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