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CPU fan won't start

Last response: in Motherboards
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June 10, 2012 10:40:15 AM

Hi,

My CPU fan is having troubles.

First of all, I have tested another fan that is known to work. This other fan works when my existing one works, and fails when the other one fails (based on brief testing). So I strongly suspect that the fan is not the problem.

Anyway, the symptoms are as follows:
* Computer sometimes suddenly reboots without warning
* Sometimes, after such a reboot, the CPU fan does not start. In this case, I hear other fans go on, but no motherboard lights, no sounds (CD drive and hard disks seem to start up). Screen remains off
* Multiple power downs, unplugging and replugging power to motherboard, switching the PSU off (has a power switch on it) seem to make no difference - fan still won't start. Have tried unplugging CPU fan and replugging it in
* Unrelated to any actions (i.e., nothing changed from previous to next try), the CPU fan will suddenly start working when I try to power it on some attempt. When the CPU fan turns on, the computer will boot

My problem is, I don't have any idea what might be causing this. So far as I can tell, it could be the motherboard, the PSU, the fan (though that seems unlikely given above test)

Any ideas on what may be the problem may be? Or how to diagnose! Trying a different PSU is the obvious next step, since it's the easiest test, but not sure I'll have one handy that's good enough! So want to postpone that.

Unfortunately it's so infrequent (maybe once every few hours), it's very hard for me to diagnose.

Computer specs:
* Motherboard - Gigabyte GA z68xp ud3 (rev 1.0 running F10 bios - updated it to test for fix)
* CPU - intel i7 2600k
* Powersupply - Corsair HX 850 W
* Graphics - 2x msi geforce gtx 560 ti
* Memory - 16GB (4 sticks) G.Skill some type I can't remember ripsaw or sniper or something, can check if needed

I think those are probably the main bits.

Thanks for your time!

More about : cpu fan start

a c 1034 V Motherboard
a c 791 à CPUs
June 10, 2012 4:04:04 PM

Sounds like it is the motherboard failing since it is it that supplies voltage to the fan.
a b V Motherboard
a b à CPUs
June 10, 2012 7:14:59 PM

What case are you using?

It sounds to me like your problems might be related to the cooling system.

Take out your 2nd video card and tell me if it still happens.
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June 11, 2012 1:00:22 AM

Thanks for the replies so far.

When it was failing at one stage, I took out the primary video card, and put the secondary one (identical model, etc) in the primary slot and tried with just one - it still wouldn't start. I now have what was the secondary in the primary slot, the primary in the secondary, and the problem has since recurred (as I said, it seems to be intermittent).

As for the case, it is a Coolermaster HAF 922M (http://www.coolermaster.com/product.php?product_id=6606). The cpu fan I'm using is the stock intel one that came with it.

Why do you think it could be the case?
a b V Motherboard
a b à CPUs
June 11, 2012 1:23:16 AM

Can you borrow a PSU from somebody?

Can you run the computer off the onboard graphics and use it without both video cards?
June 11, 2012 4:37:36 AM

rolli59 said:
Sounds like it is the motherboard failing since it is it that supplies voltage to the fan.


If indeed it is the motherboard, as I fear it may be, how would you recommend I claim warranty for it (as in, how could I argue that it is faulty)? My fear is that they will take it away and test it half-heartedly and discover no problem (as it takes hours between failures for me, and it might be triggered by the fact that I'm using it a particular way).

That is, if you have any idea how to answer my question :) 

Raiddinn, not sure if I can borrow a PSU. I may be able to try onboard graphics. Why did you think the case may be at fault?

Thanks again
a b V Motherboard
a b à CPUs
June 11, 2012 5:14:37 PM

The cooling system is very closely linked to the power system. The temperature internal to the PSU itself directly impacts the quantity and quality of power that it delivers to the system.

Every 1c higher temperature in the PSU makes the PSU perform that much worse. A bad case generally results in much higher temperatures internal to the PSU than a good case does.

As for the RMA thing, I have never heard of a broken board being returned to somebody still broken. Most of the time when they return your board to you exactly as they received it then it is because it really never was broken in the first place.
June 12, 2012 3:26:58 AM

Overheating is not the issue here - the weather is very cool here at the moment, and the computer (CPU too) has certainly not been running hot.
a b V Motherboard
a b à CPUs
June 12, 2012 4:26:55 AM

Tell me again how you know the temperature internal to the PSU or how much strain is on the PSU at any given point in time?
June 12, 2012 4:43:19 AM

Raiddinn said:
Tell me again how you know the temperature internal to the PSU or how much strain is on the PSU at any given point in time?


I don't really know, but I strongly suspect. I just notice the temperature of my room, of inside the case when I investigate the issue, touch the PSU externally and feel that it's cool, that sort of thing. But I certainly haven't used a program to monitor such a thing (if such a program exists), nor have I rummaged around inside the PSU.

I would point to the following:
a) My computer lies untouched and is just idle, when the problem can occur (it suddenly reboots and fails to start up the fan on the reboot
b) When the issue has occurred and the computer has been sitting turned off (so the PSU has had plenty of time to occur), the fan still does not start

So cooling off the PSU is not a solution to get the CPU fan to start again, leading me to suspect that the PSU being too hot is not the issue.

Unfortunately I don't have another PSU at this stage with which I can test to compare.
a b V Motherboard
a b à CPUs
June 12, 2012 1:36:11 PM

No programs exist that monitor the temperature in a PSU nor how much strain is being placed on it. There is no data cable connecting the motherboard and the PSU.

In this game you learn a couple things pretty quickly. One of those things is that PSU problems can disguise themselves as problems with anything else.

Another one is that you can't trust the results of any test if you can't trust the PSU. It is quite possible a bad PSU will cause a computer to randomly pass and fail the same test.

Anything intermittent that has to do with restarting can potentially have to do with the PSU.

This is why people here suggest testing the power system first for some huge percentage of the computer problems people come here with. It just makes troubleshooting sense. We need to be able to trust test results if we are to diagnose problems based on them.

The best way to do that is to get a PSU that gives somebody else no problems and try it in your computer. If it acts the same, then we can assume it isn't a power problem.

I would strongly advise if you have a friend or relative that does gaming that you consider asking them if you could borrow their PSU for a day.

On a separate note, I don't trust anything that says Corsair on it without examining it thoroughly and you just so happen to have a Corsair PSU.

Anyway, here is how we are going to go forward on this if you insist on not switching out the PSU:

1) Go in Windows, right click my computer, properties, advanced system settings, startup and recovery, settings, IF automatically restart is checked, uncheck it.

If you see some error coming up in lieu of a restart after this, write down everything about it that doesn't look generic. This could mean a lot of writing.

2) Take out the bottom video card, 3 of the 4 sticks of RAM, any CD drives, any data drives not useful for booting the computer, and anything else you don't absolutely need to boot into windows.

3) If you have an AC oscillating fan, take the PSU out of the case and point the fan directly into it while the computer is on.

Then turn the computer on and see what happens.
a c 1034 V Motherboard
a c 791 à CPUs
June 12, 2012 3:31:34 PM

Apolloe said:
Thanks for the replies so far.

When it was failing at one stage, I took out the primary video card, and put the secondary one (identical model, etc) in the primary slot and tried with just one - it still wouldn't start. I now have what was the secondary in the primary slot, the primary in the secondary, and the problem has since recurred (as I said, it seems to be intermittent).

As for the case, it is a Coolermaster HAF 922M (http://www.coolermaster.com/product.php?product_id=6606). The cpu fan I'm using is the stock intel one that came with it.

Why do you think it could be the case?

Sudden reboots could very well be PSU related but if it is just the fan that does not turn and everything else does then it is more likely motherboard as per my post above!
If you are meaning CPU fan does not start along with no boot then you are looking at PSU failure.
!