A few complaints have come out today that MacBook Air either doesn't go to sleep (all known models have suffered) when closing the lid or on the contrary doesn't wake from the sleep after it opening. The same complaints have been expressed earlier by the owners of MacBook Pro (early 2009 and later models) and MacBook (late 2009) It is more likely than not that reported issues are related with the failure of the System Management Controller (SMC) on MacBook Air / MacBook Pro / MacBook all Intel-based. The SMC is a chip on the logic board that controls many low-level functions including those ones related to powering of your computer.To correct its behavior all you need is to reset the current SMC data back to the original factory settings . Here are simple steps to follow for Macs with not removable battery:
You can notice that SMC has been reset by watching the LED on the MagSafe power adapter - it may change states or temporarily turn off .
For Macs with removable battery:
SMC reset will not reset the PRAM at the same time. PRAM memory stores the very basic system settings like the start up chime and display refresh rates. So its advisable also to reset this memory to its factory settings. To do this:
All above advises are also applicable when MacBook Air / MacBook Pro / MacBook won't start up after pressing the power button, when computer’s fans speed up quickly and remain at high speed / run at high speed although the computer is not experiencing heavy usage and is properly ventilated, when keyboard backlight / Status Indicator Light (SIL) / Battery Indicator Lights appears to behave incorrectly, when the display backlight doesn’t respond correctly to ambient light, when computer sleeps or shuts down unexpectedly, when the battery does not appear to be charging properly and when the MagSafe power adaptor LED appears to indicate the incorrect activity .