While your Mac will most likely give you years of service with no problems, you may find that from time to time you experience issues with your Mac’s cooling fans running at a high-speed, or your MacBook’s battery won’t charge, or it won’t even turn on. It could be all your Mac needs is to have its System Management Controller (SMC) reset.
The System Management Controller controls and manages your Mac’s system hardware controlling its power consumption, battery charging and battery function, thermal and fan activity, LED lighting for keyboards and displays, GPU functionality, sleep and wake, and other hardware functionality.
If your Mac’s cooling fan(s) run constantly at a high speed, even when no heavy lifting is being done by the CPU, you might need to reset the SMC.
If your Mac isn’t turning on, or it won’t go to sleep, or you’re experiencing random shutdowns and reboots, or your Mac’s battery won’t charge, you might need to reset the SMC.
If your screen on your MacBook or your external display isn’t working, or your Bluetooth and AirPort aren’t working, you might need to reset the SMC. Get the idea?
The method of resetting the System Management Controller on MacBooks and MacBook Pros are different, depending on if the machine has a non-removable internal battery versus a removable battery. Plus, the procedure differs for desktop Macs and laptops. So, pay attention, and don’t try to work ahead.
Note: When you reset your Mac’s SMC it will lose any custom power specific settings, like the time it takes to sleep a Mac and other customizations to power settings. So, you will need to again set any such custom settings you’ve made to you machine following the SMC reset.
Resetting your Mac’s System Management Controller should solve any of a number of minor hardware issues. If you continue to experience ongoing issues, it is always advisable to consult with Apple Support. You can also try to reset your Mac’s PRAM, which can also solve a number of minor issues that arise from time to time.
(Thanks to OSXDaily.com for the original tip)