How to reset MacBook Air SMC / PRAM

SMC RESET

  • Shut down the computer
  • Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected
  • On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time
  • Release all the keys and the power button at the same time
  • Press the power button to turn on the computer

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
  • 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

source: https://discussions.apple.com/docs/DOC-3604

in MacBook Air, Support