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I have a Asus P5Q Deluex motherboard and ever since I installed Windows 7 when I shutdown or the computer goes into Hibernate mode the fans turn on to 100%. It will be running super quiet when actually using it, then I shut it down and the CPU and the Graphics card fans go crazy.

I have had a read and cannot really see anyone with a similar problem, I am just using the standard motherboard CPU fan controller.

Does anyone have any ideas?

Just to clarify, the come onto 100% and then stay at 100% until the PC is physically unplugged or the PC is running again...

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My fans also do this, then they go quiet once it goes to hibernate. It does not seem to be an issue to me. – Simon Sheehan Jun 14 '11 at 23:14
Nope for me Hibernate, Sleep and Shut Down are all the same Hyper fans and using about 100w..... upsetting – mr copathorn Jun 14 '11 at 23:23
Could you clarify your issue a little bit? Fans hitting 100% on power-on and just before power-off is very common and is normal. Every computer I've ever seen has done at least the 100% on poweron, and most of them will throw the fans to 100% for about a second after the shutdown screen disappears and the power actually shuts off. Or do your fans turn on and stay on the entire time the computer is turned off? – TuxRug Jun 15 '11 at 4:12
They come onto 100% and never go off – mr copathorn Jun 15 '11 at 14:26
Can you specify more about your hardware and show a list of running processes for us? – kokbira Jun 15 '11 at 20:57

I know one of the servers at my school would do the same thing when booting up, before the OS loaded. I figured it was a safety feature, in that it cooled all the hardware down as best as it could until the OS could load and set the proper parameters, basically as a failsafe for when the fans weren't being managed by software.

Perhaps your system is doing similar?

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A very reasonable assumption. My guess my also be that its testing the fans before the next startup. Just a guess though. – Simon Sheehan Jun 14 '11 at 23:55
On an Asus motherboard, BIOS has a SMARTFAN feature, fan being controlled by the BIOS. It starts off 100% then the SMARTFAN feature kicks in. THe only reason it doesn't kick in at the start, is because the bootup process hasn't reached the point for SMARTFAN To kick in yet! Since you have a server like that though, you could perhaps see what happens on hibernation.. is there even a moment where they go 100%? that'd be an interesting test for mr copathorn.. – barlop Nov 10 '11 at 13:47

I guess that the problem is damaged motherboard or a broken power supply. The 100 W give it away (but even that is a lot! There are standards which regulate off and hibernate power consumption. I can't remember exact numbers, but it should be just couple of watts.). Once the computer shuts down, motherboard is supposed to release the PS_ON pin and let it float. Until it does that, the PSU will remain on and the fans will run at full speed because the fan speed control circuitry is off. It seems that for some reason your PSU does not shut down so the problem is either the power supply which doesn't detect when motherboard releases the PS_ON pin or the motherboard which doesn't release the pin during shutdown.

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Regarding bootup, that's the SMART fan option in the BIOS.

With Asus Motherboards they start up the fan on max for a moment while booting, then the SMART FAN option if enabled, kicks in and the fan goes quieter, adjusting no doubt based on temperature. I don't recall what happens on hibernation.

Try fiddling around in your BIOS.. This is a bit of a wild guess but maybe there's a setting there about power modes that causes this.

Perhaps you should look into the graphics cards fans going crazy.. if it happens on bootup too, or is something happening after "shutdown", and it's getting hot..You could try pulling the plug, touching the case to remove static, and checking the temp of the graphics card chip with your finger

Does your PC Shutdown at all? If not or regardless, try changing the PSU, or putting the PSU onto another motherboard/computer. You could also try backprobing with a multimeter, and comparing with a computer that's ok. For shutdown and hibernation.

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