Fan Constantly Running at Full Speed


When I turn on my MacBook, the fan immediately begins running at full speed and does not stop until I completely shut it down.


  • MacBook
  • MacBook Air
  • MacBook Pro


The System Management Controller (SMC) built into Macs can sometimes not recognize the fan, battery, or other hardware, and cause it to have undesired performance.


  1. Shut down the computer.
  2. Plug in the MagSafe or USB-C power adapter to a power source and to your computer.
  3. On the built-in keyboard, press the (left side) Shift + Control + Option keys and the power button at the same time.
  4. Hold these keys and the power button for 10 seconds.
  5. Release all the keys and the power button at the same time.
  6. Press the power button again to turn on the computer.

Note: On MagSafe power adapters, the LED might change states or temporarily turn off when you reset the SMC.

If an SMC reset does not fix the issue please contact the ITS Service Desk.

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Article ID: 2974
Thu 2/22/18 12:38 PM
Fri 7/7/23 2:47 PM