iMac Fan Revved Up All the Way - NOTHING Worked!

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iMac Fan Revved Up All the Way - NOTHING Worked!

Hi,

I've had a mid-2011 27" iMac (Intel) for about a year, and I am now facing the problem of having my CPU fan constantly revved up all the way (~4000RPM). I get this even when my CPU is 97% idle and the temperatures across the board (according to iStat) are perfectly normal.

Now, I've tried every possible solution I came across, and nothing worked. Among what I tried:

Resetting the SMC
Resetting the PRAM
Sleeping, restarting, shutting down, etc.
Re-installing Mountain Lion
Removing all sorts of applications and killing all sorts of processes
Using every imaginable fan control software (and I do mean /every/)
Formatting the hard drive and doing a clean install of Lion
Formatting the drive again and doing a clean install of Mountain Lion

For some reason, despite all the above "solutions" the fan still insists on revving up to above 3500RPM (usually the first few minutes or hours of running the machine after each of the solutions above works, but then the fan revvs up again for no apparent reason). In fact, the minimum CPU fan speed remains stuck at 3500 (even when I manual set it to, say, 1200, regardless of which fan control software I use).

So, do I have a hardware problem? Is it a problem with my temperature sensors? Do I need to get something replaced? My problem is that I'm currently living abroad, in a country with no Apple Store in sight, and hence no access to an Apple Genius. I really hate the idea of manually opening up my iMac and messing around with it. But is that the only option I have? Should I try to disable the fan, for example? If so, how? Check for loose wiring? What?

One final note that could be helpful: I noticed from the first or second week of using my iMac that its power supply makes a very faint buzzing sound when the machine is off (you have to place your ear next to it to hear it). Could this be a power supply issue, which hosed the temperature sensors over time?

Please help me with whatever suggestions you may have. Thank you.

iMac, Mac OS X (10.7.2)

Posted on Sep 29, 2012 9:45 AM

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Answer 1

baltwo

Level 9

62,362 points

Sep 29, 2012 12:49 PM in response to tazzouka

Contact Apple Service, iMac Service or Apple's Express Lane. Do note that if you have AppleCare's protection plan and you're within 50 miles (80 KM) of an Apple repair station, you're eligible for onsite repair since yours is a desktop machine. Might also apply to new machines the first 90 days. BTW, the AppleCare Protection Plan's the best insurance policy available for desktop machines. Get it if you don't have it before contacting Apple.

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Answer 2

RRFS

Level 5

4,522 points

Sep 29, 2012 12:57 PM in response to tazzouka

To identify potential hardware problems: Apple Hardware Test

I suspect a bad temp sensor if you aren't having actual temp issues. They do fail, do you have AppleCare? You may be able to talk Apple into repairing your unit if it is just barely 1 year old, it will require a supervisor level authorization, but I would try on the phone.

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Answer 3

tazzouka Author

Level 1

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Sep 29, 2012 1:50 PM in response to RRFS

I've tried running the Apple Hardware Test several times, but all I'd get is a lingering gray screen (while I'm pressing the 'D' key) and then after a while the OS starts up normally, bypassing the test altogether. This happens on Lion and Mountain Lion. I even tried booting off the Lion and Mountain Lion DVDs and can't find the AHT there either.

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Answer 4

baltwo

Level 9

62,362 points

Sep 29, 2012 2:07 PM in response to tazzouka

I even tried booting off the Lion and Mountain Lion DVDs and can't find the AHT there either.

Since there aren't any Lion or ML DVDs provided by Apple, that's a strange comment. For the AHT failure, assuming that the machine came originally w/Snow Leopard, try this.

Mount disc 2, run this command in the Terminal app, OPTION-click & hold Finder's Dock icon, and select RELAUNCH:

defaults write com.apple.finder AppleShowAllFiles 1

That unhides all hidden files/folders.

Now, drill down to /"Applications Install Disc"/System/Library/CoreServices/ and drag the .diagnostics folder into your Lion or ML boot volume's /System/Library/CoreServices/ folder.

Run this command to hide the normally hidden files/folders and RELAUNCH the Finder again.

defaults write com.apple.finder AppleShowAllFiles 0

This should allow the machine to boot into AHT when restarting and holding down the D key.

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Answer 5

tazzouka Author

Level 1

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Sep 30, 2012 7:36 AM in response to baltwo

I created Lion and Mountain Lion bootable DVDs, which is easily done, but for some reason Apple did away with AHT as of Lion (my machine shipped with Lion, by the way). In any case, I'll try getting a hold of a Snow Leopard DVD and running the test, although I suspect it won't work with my hardware. Hopefully, I'm wrong. Thanks for the tip.

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Answer 6

baltwo

Level 9

62,362 points

Sep 30, 2012 11:07 AM in response to tazzouka

Thanks for clarifying. The DVDs you made won't include the AHT that shipped with your machine. Since your machine shipped with Lion, I suggest that you call 1-800-MY-APPLE, or the number for your country if not in the US, and request they ship you a disc containing the AHT for your machine. AFAIK, every Mac has it installed or is included on the discs that were supposed to be in the machine, originally.

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