Fan wont stop running

Question

I updated to Mac OS X 10.4.9 this morning and the fan in my IMac has been running constantly. Is there anyway to turn it off and/or why is this happening?

Answer 1

Hi croth75!
No, you wouldn't want to shut down any fan. They're built to run to meet the demands of the system. There may be some temporary conflict of instructions within the system causing the fans to run at unusual speeds. The best way to resolve this conflict is to perform a reset or two that should re-synchronize the controllers within the system.
The first thing I would do is restart the iMac. The second thing I would do is shut down, let it sit a minute, then startup the iMac.
If the fan is still the only thing bugging you - check the System Profiler's listing of the "Boot ROM Version" and the "SMC Version" against the Firmware Update's Read-Me to verify that your Core Duo iMac's firmware and SMC firmware are up-to-date, or if you have a Core 2 Duo, you only need to check the firmware. If necessary, update the firmware or the SMC firmware (one at a time). http://docs.info.apple.com/article.html?artnum=303903
Once it's up-to-date, reset the SMC by following these instructions: http://docs.info.apple.com/article.html?artnum=303446
Since it's an absolutely no-risk procedure, it may be repeated several times until one feels certain they've done all they can with that possible solution.
If it's then necessary to find another solution, try a single PRAM reset. It's NOT something you would do every day - but to reset the PRAM:
1. Shut down the computer.
2. Locate the following four keys on the keyboard: Command (Apple logo), option, P, and R. You will need to hold these four keys down simultaneously in step 4.
3. Start up the computer.
4. Press and hold the Command-option-P-R keys. You should press this key combination immediately after the startup chord sounds, and certainly before the gray screen's Apple logo appears.
5. Hold all four keys down until the computer restarts and you hear the startup chord for the second time. The PRAM reset will reset your sound level preference to the mid-point, so the second time may well sound more or less loud than the first.
6. Release the keys.
Also probably reset will be Startup Disk in System Preferences.