Fan Rattling, Mouse and Keyboard Glitching...

Hello everyone,

It seems I have a problem with my Late 2012 27" iMac and I could not find anything similar anywhere on the internet. Hopefully one of you fantastic people can help me out here because this problem keeps bugging me a lot.

It all started around four days ago when the Mac suddenly made a pretty noisy rattling sound, as if the cooling fan was really stuttering. This did not seem to be the case however, as it was resolved by a reboot. However, the odd sound was paired with mouse and keyboard glitches - specifically, the mouse tried to select a random menu option whenever a menu was opened (for example, whenever I clicked on the Apple logo in the upper-left corner, the mouse glitched out between where the pointer was and the 'About This Mac' option). Also, whenever a program with a textbox was opened (for example, System Settings or Safari), the computer automatically entered four zeroes in the textbox, and when trying to type in it the Mac tried to add some more zeroes after it. So you basically can not use any internet browser since it would always try to type '0000' instead of any web address.

The odd thing is that the issue is resolved by rebooting, but keeps occurring whenever a basic task is executed (anything like opening Mail or Safari makes the Mac glitch out). Not to mention this is one of many odd one-of-a-kind problems the device has had since its purchase in the summer of 2013, for example: the most recent update wouldn't install via the App Store but instead it had to be done manually via the Apple Support center, downloaded via another Windows PC because the .DMG I downloaded on the Mac was always 'damaged' in some way.

Normally I would have tried to find a solution to the problem by resetting the Mac entirely, but since my parents operate this device more than I do myself, I may have to try softer measures first. I've checked the list of recently downloaded files and software but this is limited to a couple of SoundCloud MP3's and business PDF files. No software has recently been installed (at least not by myself, but the recently added programs prove that nothing has been installed since two months or so, long before the problem occurred), the most recent program being 5kPlayer which does not seem like anything harmful to me honestly. I tried setting back the time machine to a point where the problem was not persistent (about two weeks ago), but it was triggered again when the standard Mail application was executed.

Some other factors that may help narrowing down the range of possible causes:

• The Mac is positioned right under the staircase, but little dust comes off since every step is closed off by wooden planks to protect the Mac. On the desk stands another laptop in a charging dock, Harman/Kardon speakers and some papers and bills. Anything magnetic has been removed for a long time, since the Mac also has got smudges at the down-left and right corners of the screen that may have been caused by magnetic interference (but honestly it came out of the box like that so I do not quite believe this statement)
• The Mac has never been opened up (before) and no additional hardware, aside from external hard-drives and an external Blu-Ray Player, was added to the system.
• The Mac does have quite a lot of software installed on it, yet I don't see any link to the recent issue with that. As said, no software was recently installed, and the last update was installed about three weeks ago - two weeks before this problem occurred.

If any more information is required, I'm keen to help out!

Kind regards,

Rick

Sorry for my poor English, it's not my native language..