imac makes strange ticking noise even when it's turned off

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Try checking the hard disk for errors just in case.
Open Disk Utility, in the Utilities folder in the Applications folder.

Insert your Mac OS X Install disc in your computer’s optical drive or an optical drive connected to your computer, and then restart your computer. When you hear the startup tone, hold down the C key until you see the progress indicator, which looks like a spinning gear.

Follow the onscreen instructions until the menu bar appears with the Utilities menu in it, choose Utilities > Disk Utility, click First Aid, and then click Verify. Of Disk Utility reports errors, click Repair. When it's finished, from the Menu Bar, select Utilities/Startup Disk. In the Startup Disk window select MacintoshHD 10.x.x and click Restart.

Also, while you have Disk Utility open, Repair Disk Permissions, reboot and see if the sound anomaly still exists.



Carolyn 🙂

Turn the computer off and unplug it. If the ticking noise stops it might be a good idea to call Apple about it. There might be an electrical issue that needs to be fixed. If unplugging it doesn't stop the ticking then I think your ticking noises are due to the thermal dynamics of heated components contracting as they cool (unless maybe you've made someone angry enough to leave a little ticking package in your computer.)

thermal thing would not be continous i guess.

I'd think it wouldn't continue more than a few minutes.

I'm guessing you are correct that it is a capacitor discharging.