* Issues with your Mac cooling fans and fan management: the 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
This is how to reset SMC on most modern Mac laptops, none of which have a removable battery:
Here is how you do it :
Older MacBook laptops, indicated by having a removable battery, can reset SMC with the following approach: