What kind of iMac is it?

It's a 20" iMac G5 1.8GHz I started using around January 2005.. I don't think it's the heat of the processor since this is the first time it does that since I started using it, not to mention the air coming out at the back is practically room temperature and not hot.

Waleed
www.waleedsgallery.biz

This happens every so often with my powermac G5. I found that my room is a little dusty and after a while the fans suck up a lot of dust into the tower. I openned up the tower and cleaned up the dust and the fans stopped firing up so loudly. I'm not sure if this is the same with iMac's. Best of luck with this problem.

That's worth a try RichG, thanks.. We've had a very dusty weather for the past week..

Waleed
www.waleedsgallery.biz

Well if it's an original model, then maybe you should take it to the service (assuming that it still has a warranty) - this is a well known problem on these...

Almost a year and a half, I think it passed its warranty.. A phone call wouldn't hurt.. Many thanks..

Waleed
www.waleedsgallery.biz

It result in the fan failure, so I changed it and problem resolved, but it was very dusty, so try to clean it before it burn the fan, good lock.
Roberto.

i have the same issues with my pc.
because of the dust, fans get very noisy and they spin slowly.
i had to clean them too and it was definetly better.
but soon i'll have to replace them.
once they start going nuts, its only a matter of time.

twice a year I have to completely strip down my computer and clean everything. no matter how good the case is sealed, the dust keeps
getting in. its not a matter of electricity problem, since dust is somehow
an isolator. but its a problem with temperature and blockin air flows.

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always outnumbered, never outgunned

I've always had a lot of luck with MacInTouch www.macintouch.com. Its a web site with posts of Mac People and their problems. I queried "iMac G5 Fan Noise" and found these search results: http://www.macintouch.com/imacg5part05.html

You may also try "repairing the permissions." To do this restart the computer with the start up disk that came with the computer and choose the "Disk Utility" from the menu (before you install the software). I had a G5 Xserve once that would not shut up with the fun noise. It had crapped out during the weekend due to a power failure. The problem was not the fan itself. It was the processor "panicking" at startup. This is also something I find with my Mac Mini. It will sound like a Jet Engine sometimes. I realize all of a sudden that I have 23 Safari Windows open. Once I shut them all down it stops.

I've also experienced problems with third party software like the HP software for a scanner. If the software is causing "panics" it can raise the work of the processor and thus rev the fan. It wouldn't matter what program you were working in. It happens in the background. A good way to see how much your processor is being taxed is to use the "Activity Monitor" found in your Utilities folder. You can see how much work each program is giving the processor.

My 20" Imac did the same thing. Finally it evidentally go hot enough to shut itself down. I ended taking it in (thank gawd for Apple Care). They said the power supply on the back got too hot and fried. So after replacing it twice and then also having to replace the hard drive (of course nothing from my old hard drive was salvageable).

MIght have it checked out just in case -

Sorry to bump up the thread..

Just minutes ago, I decided to install the nagging iMac G5 sleep-light that Software Update have been popping in my face every time it ran. It gave me a warning that a shutdown needed after it updates the firmware, during the update the fan will run at full speed but will resume normal speed after the update is done..

Ta daaaa... How I miss this silence when I work.. The update is done.. The fan is off.. The iPod SoundDock is back to normal whisper volume.. :)

Waleed
www.waleedsgallery.biz