You’ve tried rebooting, you’ve reset the PRAM, you’ve done it all, but your Mac is still behaving strangely. What next? In certain circumstances, try resetting your Mac’s System Management Controller (SMC). This is sometimes necessary to restore normal lower level system functionality to your Mac, particularly if you’re having these types of problems:
* Issues with your Mac’s cooling fans and fan management: fans run constantly at high speed, fans run high despite low CPU usage and adequate ventilation, fans not working at all, etc
* Power management and battery problems: Mac isn’t turning on, sleep isn’t working, random shutdowns and reboots, battery isn’t charging, Mac won’t wake from sleep etc
* Light problems and improper lighting management: battery indicator lights aren’t working, display backlighting isn’t adjusting to ambient light changes, keyboard backlights not working, etc
* Video and external displays not working: display brightness functionality not working properly, target video mode isn’t working properly, external display isn’t working, etc
* General performance and functionality problems: abnormally sluggish behavior despite no CPU or disk usage, external ports not working, airport & bluetooth aren’t showing up, external devices are not being found, etc
So now that you’ve concluded you need to reset your SMC (Note that the SMC is on Intel Mac’s only), here’s how to do it on MacBook’s, MacBook Pro’s, iMac’s, Mac Mini’s, and Mac Pro’s. Notice that the reset instructions are different for MacBook and MacBook Pro’s if you have an internal or detachable battery.
Reset the SMC of a MacBook or MacBook Pro’s with detachable batteries:
* Shutdown the MacBook/Pro and remove the battery
* Disconnect the power adapter, hold the Power Key for 10 seconds
* Release the power key and reconnect your battery and power adapter
* Turn your Mac on
* Let boot as usual.
Reset SMC of a MacBook or MacBook Pro’s with an internal battery:
* Shutdown your MacBook/Pro
* Connect the power adapter to your Mac
* On the MacBook/Pro’s keyboard, hold down the Shift+Control+Option keys and the Power button at the same time
* Release all keys and the power button at the same time
* Boot your Mac as usual
Reset SMC of an iMac, Mac Pro, Mac Mini:
* Shut down your Mac
* Disconnect the power cord
* Press and hold the Mac’s power button for 5 seconds
* Release the button
* Reattach the power cables and boot the Mac as usual
Hopefully that will clear up your problems, if not it might be worth a visit to the Apple Store or a certified repair center.