Fan racing and won't sleep - please help

Question

I have a 2.16 Ghz Intel 24" iMac. Recently I began to have the following problem. Once I use it for awhile and it starts to get hot, the fan activates on high. As a result, the computer will never go to sleep. Even if I try to put it to sleep manually, the display darkens but it immediately wakes up again and won't go to sleep without a shut down. I read all of the postings on this and can't find anything similar. I also should mention I have nothing but an Apple wired keyboard and mouse connected, along with an Ethernet connection to a TimeCapsule. In settings, "wake on Ethernet" is off and there are no apps in the start-up chain. I also verified and repaired permissions. If anyone has any ideas I'd greatly appreciate them. Thanks.

Answer 1

Redo the SMC reset, in addition to unplugging the power cord from the back of the computer (not the wall!!!!!!) unplug all peripherals such as external HD's, keyboards, mice, printers etc... When you re-start the computer only plug in the keyboard and mouse.
If that still does not solve the problem do a PRAM reset by:
_PRAM RESET_
• Shut down the computer.
• Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
• Turn on the computer.
• Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
• Hold the keys down until the computer restarts and you hear the startup sound for the second time.
• Release the keys.
Repost what occurs after you done both the SMC and PRAM resets.
Regards,
Roger