Apple iMac G5, 20-inch - Manual (Page 272)

48 - iMac G5, 20-inch Troubleshooting Symptom Charts
5. Power off your computer, remove the power cord and any other cables that are
connected to your computer and remove the back cover.
- Plug the computer in and start it up by pressing the internal power button.
- As the machine starts up, listen carefully to each of the fans, and see if you can
locate one of the three fans of which the objectionable ticking, whistling, or squealing
sound is coming from.
Can you pinpoint the fan making the sound?
Yes: If the sound is coming from one of the fans near the hard drive, you can order
and install the Upper Fan kit for the computer.
If the sound is coming from the fan near the power supply of your computer, you
should order the lower fan.
No: If you can hear an objectionable ticking, whistling, or squealing sound, but you
cannot identify the source of the sound, contact Apple Technical Support.