SMC Reset

As stated on Resetting the System Management Controller (SMC) on your Mac - Apple Support

In some situations you might need to reset your computer's System Management Controller (SMC). Learn how to identify these conditions and to reset the SMC on Intel-based Macs.

The SMC is responsible for many low-level functions on Intel-based Macs. These functions include:

• Responding to presses of the power button
• Responding to the display lid opening and closing on portable Macs
• Battery management
• Thermal management
• The SMS (Sudden Motion Sensor)
• Ambient light sensing
• Keyboard backlighting
• Status Indicator Light (SIL) management
• Battery status indicator lights
• Selecting an external (instead of internal) video source for some iMac displays

Some indicators are:

Fans

The computer's fans run at high speed although the computer is not experiencing heavy usage and is properly ventilated.

Lights

• The keyboard backlight appears to behave incorrectly (on Mac computers that have this feature).
• The Status Indicator Light (SIL) appears to behave incorrectly (on Mac computers that have an SIL).
• Battery indicator lights, if present, appear to behave incorrectly (on portables that use non-removable batteries).
• The display backlight doesn't respond correctly to ambient light changes on Mac computers that have this feature.

Power

• The computer doesn't respond to the power button when pressed.
• A portable Mac doesn't appear to respond properly when you close or open the lid.
• The computer sleeps or shuts down unexpectedly.
• The battery does not appear to be charging properly.
• The MagSafe power adaptor LED doesn't appear to indicate the correct activity.

System performance

• The computer is running unusually slowly although it is not experiencing abnormally high CPU utilization.
• Application icons may "bounce" in the Dock for an extended amount of time when launched.
• Applications may not function correctly or may stop responding after being opened.

Video

• A computer that supports target display mode does not switch into or out of target display mode as expected.
• A computer that supports target display mode switches into or out of target display mode at unexpected times.

Port illumination

The illumination around the I/O ports on a Mac Pro (Late 2013) does not activate when you move the computer.

And no, It won't erase any personal files.

Hello dathappsheep,

What it will erase are a few personal settings, like fonts but nothing that can't be re-set in a minute or so.