iMac fan runs when sleeping or off

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Help! This is the second time this has happened to me and I can't find answers anywhere.

A new iMac I plug in works fine, then the fan runs full speed, but ONLY when the Mac is off or in sleep mode. When on, it's silent and works a treat.

Have it plugged into a surge protector. It must be some electrical problem. Can I manually make the fans stay off when sleeping/off?

Thanks in advance.
 
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Hi,


the fan runs full speed, but ONLY when the Mac is off or in sleep mode.

Pull the AC cord out of the wall outlet. That way you know it is shut down. Give it a few seconds and then plug it back in. If you hear the fans spin up then you have a hardware problem.:(

A new iMac I plug in works fine,

Its new so get in touch with your nearest Apple shop and book it in ASAP.
 

Cory Cooper

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Hello and welcome.

-Which exact model iMac?
-Which version of OS X?
-What Login Items are listed in  > System Preferences... > Users & Groups > your login > Login Items?
-Do you have any third-party utilities like MacKeeper/CleanMyMac or an antivirus app installed?
-Do you have any external hard dries or other devices connected?

It sounds to me like it is not actually sleeping or powering off. The fans cannot run if the iMac is powered off, as there wouldn't be any power supplied to them. In addition, if the iMac fully enters sleep mode, the fans would also not run. The fans/sensors are controlled by OS X, so if the drivers aren't loaded, they will ramp up to full speed to protect the internal components. Your screen may be turning off, but the iMac is actually hanging in a state between on and sleep/power off.

I would try these two steps to see if it cures the issue:

Reset the System Management Controller (SMC) on your Mac
How to Reset NVRAM on your Mac

Let us know if that doesn't cure it,

C
 
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I'd love to offer an opinion, but first I've got to get de-confused. I see an iMac, a surge protector, a wall outlet, and a fan. Please tell me what is connected to what, and how?
 
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All I know is that many people seem to be having fan issues with iMacs. I've seen many threads with users complaining about very loud fans. I suspect it's not a problem with your electricity or apps etc, but with the iMac itself. If it's an option I would at least consider returning it and demanding a new one that doesn't have mysterious fan issues. You really shouldn't have to spend endless hours diagnosing and fixing Apple's problems, if that's what it is.

I recently bought a 5 year old iMac and so far it's totally quiet, no fan issues at all. New or used, it's always a luck of the draw crap shoot roll of the dice situation.

However about 15 years ago I had an iMac that got so hot the graphics card melted on to the logic board (i think that's what the repair guy said) killing the machine. Just out of warranty wouldn't you know. I wound up installing that Mac in my garbage can, $2000 down the drain. Haven't bought anything from Apple since.
 

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