How to Manually Force a Mac ‘SMC Reset’ (Fix Fans Running at Full Speed)

If you own an Intel-based Mac, it utilizes a dedicated hardware chip on the logic board called the System Management Controller (SMC). The SMC is responsible for managing low-level physical functions, including battery charging, thermal management (cooling fans), keyboard backlighting, and the power button. If the SMC firmware crashes, your Mac will exhibit bizarre hardware symptoms.

The most common symptom of a crashed SMC is your Mac’s cooling fans spinning at 100% maximum speed—sounding like a jet engine—even when the computer is completely idle and cool to the touch. Other symptoms include the battery refusing to charge, or the Mac failing to wake from sleep when you open the lid. You cannot fix this by reinstalling macOS; you must manually force the SMC chip to reboot.

How to Manually Force a Mac SMC Reset

The method to reset the SMC depends entirely on whether your Mac is a laptop or a desktop, and whether it has a T2 Security Chip.

For MacBooks with a T2 Security Chip (Models from 2018 to 2020)

1. Shut down the Mac completely.
2. On the built-in keyboard, press and hold the following three keys simultaneously: Control (on the left), Option (on the left), and Shift (on the right).
3. Keep holding all three keys for exactly 7 seconds.
4. Without releasing the three keys, press and hold the Power button as well.
5. Hold all four keys together for another 7 seconds. (Your Mac might turn on and back off during this time—this is normal).
6. Release all keys, wait 5 seconds, and press the Power button to turn the Mac on.

For Older MacBooks without a T2 Chip (Models from 2017 and older)

1. Shut down the Mac.
2. On the left side of the built-in keyboard, press and hold Shift + Control + Option.
3. While holding those three keys, press and hold the Power button.
4. Hold all four keys for exactly 10 seconds.
5. Release all keys and turn the Mac on.

For Mac Desktops (iMac, Mac mini, Mac Pro)

1. Shut down the Mac completely.
2. Unplug the physical power cord from the back of the computer (or from the wall).
3. Wait exactly 15 seconds.
4. Plug the power cord back in.
5. Wait exactly 5 seconds, then press the Power button to turn the Mac on.

Once your Mac boots back up, the SMC chip will be factory reset. The jet-engine fans will immediately spin down to a whisper, and your battery will begin charging normally again.

(Note: Apple Silicon Macs with M1/M2/M3 chips do not have an SMC. The chip is integrated into the main processor. If you experience these issues on an Apple Silicon Mac, simply shutting it down and leaving it off for 30 seconds performs the equivalent reset.)