Fan at max speed, vertical lines, burning smell
My Early 2009 iMac (3.06 GHz Intel Core 2 Duo) has recently had an extremely loud fan. Using a fan utility I can see that its the CPU fan that is running at max. After a period of time, the screen will go to vertical lines and fan is off. I'm wondering what makes the fan run high in the first place- and why does it shutoff eventually?
How can I diagnose? I'm unable to boot into diagnostic mode, that appears to be something added in later models.
Is this a good question?