How To Fix Overheating & Fan Noise After Upgrading to Mac OS X 10.7 Lion with SMC Reset

A fair amount of users are reporting that upgrading to Mac OS X Lion has caused their Macs to run hotter in general and their fans to constantly engage, creating excessive and unusual fan noise. For users who have just performed an upgrade from 10.6, this is usually because of Spotlight and the mdworker & mds process combination, which irons itself out over the course of an hour or so.

If waiting it out hasn’t resolved the heat and fan noise for you, or those Spotlight processes aren’t running, you might want to try resetting the System Management Controller, or SMC. This seems to be particularly effective for MacBook Pro and MacBook Airs that are running hot with considerable fan noise after the Lion installation.
Fix Fan Noise & Heat in OS X Lion by Resetting SMC

For MacBook, MacBook Pro, and MacBook Air models with internal batteries:

• Shut down your Mac 
• Plug in the MagSafe adapter 
• Press and hold Shift+Control+Option+Power button at the same time 
• Release all keys and buttons simultaneously 
• Press the power button to turn on your Mac as usual 

Apple notes that the little LED light on the MagSafe adapter may change colors or states, or even briefly turn off when you reset the SMC, which could be an easy way to tell if it’s be done successfully.Resetting the SMC is a fairly common trick to fix some of the quirkier power and battery related problems on a Mac, and in many cases it works. If all else has failed, try this out, it just may solve your heat and fan noise issues with Lion.

Note: Anytime the SMC is reset you will typically lose custom power settings, so be prepared to go back into System Preferences to readjust Energy Saver settings again.

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