I've been having intermittent fan speed and high CPU temperature when my CPU usage is nearly 0%. I don't run any weird apps. If I put my computer into sleep mode and wake it back up, this fixes the issue. I think this is an System Management Controller(SMC) issue, but I'm not sure. Anyone know how to fix this permanently?

2 Answers 2


Try resetting the SMC as noted in the question for your MacBook Air and see if the problem persists.

If the problem does persist it may be a failing temperature sensor, resulting in the fans running faster than normal to worst case fail-safe full-speed state, your only option at that point would be to take it to Apple Support for repair / replacement.

  • Thank you @MrDaniel. I don't think it's in fail-safe because that's usually on/off which means maximum speed, however, it's not maximum speed. I'd say it's about 40% speed.
    – EhevuTov
    Commented Aug 3, 2012 at 19:13
  • 2
    Still could be a failing sensor reading hotter than it actually is, if the SMC reset is not fixing it, than something with hardware / sensors might be going wonky.
    – MrDaniel
    Commented Aug 3, 2012 at 19:18

If its a laptop, spin it upside down and blast some air into the vents. The idea is to blow out any dust that may be causing the computer to overheat.

I usually just take a deep breath and give it a good blasting...

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