# iMac Fan Starts up at Full Speed



## Keawolf (Dec 4, 2010)

My iMac has been running solid for two years now, and all of a sudden, the fan started running at full speed. It just runs constantly, all the way until I turn it off.

Unplugging the power cord, and waiting 15 seconds for the reset, does nothing for this problem.

I did a system restore with Time Machine, which fixed this problem for a few days, but now it's back to running on full speed.

The CPU is NOT being stressed at all. It's usually just sitting at 98% idle. So there's no heavy programs running.

The fan running at full speed, doesn't affect usage of my Mac; it is just strange to hear the fan like that.

The repair tool also says that everything on the volume seems to be okay.


Where I live, there is a lot of moisture in the air. It doesn't help that it has been raining for the past 3 weeks straight. 

The only possibilities I see, is either the fan kicks on to remove the moisture inside of it, or maybe this is cause by a virus?

A restore with Time Machine, did temporarily solved the problem, but it picked back up within a couple days.

I can't take my computer for repairs, and I can't call Apple support as my computer is beyond warranty.

Is there anything else I can do for this?


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## m00k (Jul 20, 2005)

That 15 second power cord thing is what usually fixes the problem, so that's pretty weird. This is a wild guess, but maybe turn off the iMac, remove the power chord, then press and hold the power button just in case there's some electricity lingering in there. I once accidentally hit the power button on my NES 10 years after last playing it and it turned on for a second. So maybe there's some power still in there that isn't allowing the System Management Control to reset.


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## Keawolf (Dec 4, 2010)

Unfortunately, no matter what I try to do with turning it off, removing the power cord, and pressing the button, it still never fixes the problem. I've left it without power for an hour, plugged it back in, waited another hour, boot it up, and still has the fan running full speed.

I fixed the problem for a few days be using Time Machine, but just for a few days and its back to the full speed fan.

My only thought now is that my computer might have moisture inside it, because sometimes, after the fan runs for a good hour or so, I can reboot the computer, and then fan will have stopped.

The area I live in is between a beach, and a rain forest. Everything gets very damp.


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## Headrush (Feb 9, 2005)

If you know your Mac temps are OK, maybe try manipulating it with iMac Fan Control. http://www.derman.com/iMac-Fan-Control


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## m00k (Jul 20, 2005)

Have you ever upgraded the hard drive? I just found out that recent iMacs go haywire if you try to upgrade without going through Apple....


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## Headrush (Feb 9, 2005)

m00k said:


> Have you ever upgraded the hard drive? I just found out that recent iMacs go haywire if you try to upgrade without going through Apple....


Yes my 2007 iMac.

The 2011 iMacs can't be just swapped with a standard HD any longer. Apple has modified the SATA power connector to include temperature monitoring feature and replacing the HD with a standard will cause the fans to run full speed. The iMac would also fail the Apple Hardware Test.

This shouldn't be a problem for your iMac though, didn't you say it was running fine for years?


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## m00k (Jul 20, 2005)

I heard that as far back as 09 models, there's some sort of firmware only found on Apple-supplied drives. Not having that firmware makes fans go nuts.


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## Headrush (Feb 9, 2005)

m00k said:


> I heard that as far back as 09 models, there's some sort of firmware only found on Apple-supplied drives. Not having that firmware makes fans go nuts.


Depends on whether yours is an early or late 2009 model.

This might help: http://www.amfiteatar.org/content/view/155/57/lang,en/

Seems using a WD hard drive works on newer models. (late 2009+)


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