Fix Fan Noise & Overheating After Upgrading Mac OS X with an SMC Reset

Sep 20, 2011 - 26 Comments

Fix fan noise and overheating with Mac OS X Lion A fair amount of users are reporting that upgrading Mac OS X has caused their Macs to run hotter in general and their fans to constantly engage, creating excessive and unusual fan noise. For users who have just performed an upgrade from 10.6, 10.7, or 10.8, this is usually because of Spotlight and the mdworker & mds process combination, which irons itself out over the course of an hour or so.

If waiting it out hasn’t resolved the heat and fan noise for you, or those Spotlight processes aren’t running, you might want to try resetting the System Management Controller, or SMC. This seems to be particularly effective for MacBook Pro and MacBook Airs that are running hot with considerable fan noise after the OS X installation.

Fix Fan Noise & Heat in OS X by Resetting SMC

For MacBook, MacBook Pro, and MacBook Air models with internal batteries:

  • Shut down your Mac
  • Plug in the MagSafe adapter
  • Press and hold Shift+Control+Option+Power button at the same time
  • Release all keys and buttons simultaneously
  • Press the power button to turn on your Mac as usual

Apple notes that the little LED light on the MagSafe adapter may change colors or states, or even briefly turn off when you reset the SMC, which could be an easy way to tell if it’s be done successfully.

This tip was left in our comments recently and several readers have responded or emailed us with positive results. To give further backing to the solution, Apple’s support doc lists the following as the first reason to reset the SMC: “The computer’s fans run at high speed although the computer is not experiencing heavy usage and is properly ventilated.

Resetting the SMC is a fairly common trick to fix some of the quirkier power and battery related problems on a Mac, and in many cases it works. If all else has failed, try this out, it just may solve your heat and fan noise issues after updating OS X.

Note: Anytime the SMC is reset you will typically lose custom power settings, so be prepared to go back into System Preferences to readjust Energy Saver settings again.


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Posted by: William Pearson in Mac OS, Tips & Tricks, Troubleshooting


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  1. paul says:

    Even in 2020 this works haha…. Thanks!

  2. Naseef says:

    I love you William Pearson

  3. andy bee says:

    works. fixed a roaring fan on macbook pro.

  4. Ruth says:

    It works!!!! Thank you thank you!!!

  5. TJ says:

    1st gen mac book air. OMG this worked, my fan would run constantly for playing videos or games, didn’t know this was the issue. Thanks for this post!

  6. Cornelius says:

    Mountain Lion:

    Resetting the SMC worked… that is all I can say.. os 10.8.2

  7. Tracey says:

    Thanks so much for this info! My fan sounded like it was dying a slow and painful death. I even opened up my laptop and blew out the dust. I tried this and started her up and was delighted to hear it sound like its old self! THANKS!!! :)

  8. Aoife says:

    Wow resetting the SMC actually worked!

  9. Aamir says:

    2 days of madness and multiple reinstalls later, this fixed it!

    I am running: Macbook Pro 13″ 2010 model (Macbook7,1) on Lion. My CPU usage has been REALLY high and in Activity Monitor, kernel_task was running wild and hogging all my CPU.

    Resetting the SMC fixed the issue!

  10. Dante says:

    Thanks a lot! U saved my life! Worked for me!

  11. Randy says:

    I have a 2007 Macbook Pro with Snow Leopard that has been exhibiting the fan problem on and off for a while now. I have reset the SMC once before which seemed to work and have just done again with instant success.
    Just hoping it stays alright for a while this time.
    On a slight tangent, after I upgraded to Snow Leopard the laptop would continue to run even though the lid was closed. This caused me much distress on quite a few occasions as it had been in a nice snug laptop bag and got very very hot several times, I am just hoping that it has not sustained too much damage. I try to shut it down now when travelling.

  12. I have just upgraded to 10.7.3 and the Fan Noise is still there when the computer is running idle. Only solution is to shut it down (not restart) and wait 5 sec. before booting – and then it keeps quiet unless I visit a website with flash.

    Seems to be a problem whenever I close the lid and open it again – Must be a software issue…

    I have a Macbook Air model 2011 with all the bells and whistles.

  13. Christopher says:

    Just did this and it’s working!

    2008 Macbook Pro, just upped to Lion
    5000rpm fans and 74C running nothing but Safari
    Did the reset
    Now a reasonable 58C and 3000rpm fans

    It’s bonkers, but it did work.

  14. feenix says:

    i have upgraded my mac to lion but its getting 2 long in startup..can anybody no whats wrong..m new at this stuffs

  15. steve says:

    i had a similar problem with new macbookpro, installed Lion and then fan started to kick in lots and became very very hot, it never did that with snow leopartd

    installed ‘gfxCardStatus’ and set it to ‘integrated only’ which means basically that the machine never uses the discreet graphics card. it worked. machine never gets hot, even when watching video, and i dont hear the fan.

    all i can think is that the new lion os x does not switch from discreet to integrated when needed. its just always on discreet and hence machine was overheating when performing intensive tasks like video or flash

    hope this helps


  16. vdiv says:

    Not to be a pain but I have never had to do anything like that on a ThinkPad or a Lattitude. Sure they get warm and noisy, but 210 deg F?!? My 2010 15″ MacBook Pro regularly heats up above 80 deg C so I use smcFanControl to keep the fan going at a minimum of 4000 rpm instead of the default 2000 rpm. This keeps it at around 65 deg C. I expect the fan to die within a year.

    Is resetting the SMC a standard operation procedure for MacBooks?

    By MagSafe adapter, you do mean the AC power supply/adapter, right?

    • OSXDaily says:

      Yes resetting the SMC is a fairly common troubleshooting technique with power related issues. And yes, the MagSafe adapter is the magnetic AC Adapter.

      If your Mac is running that hot, give it a try.

  17. Mike says:

    Reseting SMC _and_ PRAM solved more problems than just overheating and increased fan rpm. After clean installation of Lion my MacBook kept reacting sluggish, it rendered a huge usage of memory and slow release of memory. I’d been thinking to get back to SL but before doing that I tried to reset both SMC and PRAM. After reseting both my MacBook improved in usage because of speed and memory usage. Heat keeps below 195 F, even when using apps which use both CPU and video at most.

  18. Jason says:

    That would have been nice to know before my Macbook Pro did cooked itself a few weeks ago as a result – thanks apple for nothing!

  19. Joseph says:

    I’ve had the opposite happen where my Macbook gets to 210F and the fans are still going at 2000RPM. See if this works.

    • Louis says:

      210?? Reset the SMC and if that doesn’t solve it, go back to Apple, that thing is going to melt itself down!!

      • Joseph says:

        Yup according to istat sometimes higher! So did a reset, re-did thermal paste (Apple used too much) and seems okay now. Converted some video got to 170F. Way better!

        Also on older Macbooks to reset SMC you just unplug, take out the battery and hold the power button for 5 seconds.

        • rascal01 says:

          Could you maybe tell me how old an ‘older macbook’ more or less should be?
          I’ve got one dating from early 2008. I’m not sure if that would classify as an older or a newer macbook.

          • Joseph says:

            I have a late 2008 Macbook Pro I consider it older, also pre-unibody models people call “old” now.

  20. Jim says:

    Also when you perform an SMC it reset your terminal settings for verbose mode if set…

  21. Aaron says:

    I discovered this accidentally a few weeks ago on an iMac when I was moving it from one room to another. Apparently if you just unplug from the wall for like 20 seconds then reconnect and wait about 10 more to boot up it resets the same power controller. Imagine my surprise when moving the iMac from one room to another seemingly fixed the fan blaring, LOL.

    I think Apple could alleviate a lot of headaches and support calls if the power settings were trashed automatically on the first reboot of a Lion install, since this obviously is the culprit here.

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