Fans are running high and CPU is hot but I'm not doing anything..

Discussion in 'MacBook Air' started by laserbeam273, Oct 29, 2012.

  1. laserbeam273 macrumors 6502

    Sep 7, 2010
    My CPU is currently hovering around 70-75C, and my fans are working pretty hard to keep it at that (4000 RPM). Though at the moment I'm doing minimal web browsing and some very light programming. I'm using Eclipse to run some basic Java code (takes a fraction of a second for the code to run). It's sitting on a flat wooden table. No I don't have any huge processes running invisibly - my CPU is only around 2-4% utilisation.

    When I run something very intensive, e.g. a Geekbench stress test, the temps are only around 90C, so that's normal.

    This has happened before, but only in the past week whereas I've had this for months. I doubt this is how it should be, I'm wondering if any of the CPU thermal paste or fan has been shifted, as I carry my MBA everywhere with me. It's a 2011 refurbished.
  2. Mercenary macrumors 65816


    Sep 17, 2012
    Reset the SMC

    Shut down the computer.
    Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
    On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
    Release all the keys and the power button at the same time.
    Press the power button to turn on the computer.
    Note: The LED on the MagSafe power adapter may change states or temporarily turn off when you reset the SMC.
  3. zhandri Suspended

    Sep 4, 2012
    if the SMC reset doesn't help:

    i had the same problem on my 2008 macbook pro. i opened it and there was a super thick layer of dust covering the fans exit so the air couldn't get through to the copper strip which cools the CPU and GPU. if you are out of warranty you can open it up yourself and clean the fan
  4. Stingray454 macrumors 6502a

    Sep 22, 2009
    Or just check the Activity Monitor what's taking up CPU. My guess is your light browsing contains some flash animations. Even small ads made with flash can take a ton of CPU. When I started using AdBlock I increased my battery time by a LOT ;) Worth a look.
  5. GGJstudios macrumors Westmere


    May 16, 2008
    You may have more running than you realize. Follow every step of the following instructions precisely. Do not skip any steps.
    1. Launch Activity Monitor
    2. Change "My Processes" at the top to "All Processes"
    3. Click on the "% CPU" column heading once or twice, so the arrow points downward (highest values on top).
      (If that column isn't visible, right-click on the column headings and check it, NOT "CPU Time")
    4. Click on the System Memory tab at the bottom.
    5. Take a screen shot of the entire Activity Monitor window, then scroll down to see the rest of the list, take another screen shot
    6. Post your screenshots.
  6. laserbeam273 thread starter macrumors 6502

    Sep 7, 2010
    Thanks for the reply, I'll take a screen shot next time it happens.
  7. laserbeam273 thread starter macrumors 6502

    Sep 7, 2010
    Thanks for the help. I think the SMC reset has fixed this, though it may take a bit more usage before I'm fully confident of this. It definitely was running too hard for what I've been doing.

    Regardless though, here's a screenshot of my activity monitor:


    Sorry I haven't got a screen shot of what's lower, but I think this is enough to get the idea of it. It's all pretty lightweight stuff, I supposed I had a bit of wired RAM, but I don't think that should cause the fans to need to spin up hard.

    Attached Files:

  8. laserbeam273 thread starter macrumors 6502

    Sep 7, 2010
    Seems to still be a problem. CPU is only at 5% utilisation (where 100% is full, not 400%), CPU temp is 65-70C, and fans are at 5.9k RPM. My iMac says ambient temperature is 29C and it's CPU idling around 39C, fans dead quiet.

    Would I really need to reset my SMC again? I'm really hoping Air's don't run this loud usually... we're getting into summer, and I fear that once it's 40 C, my fans will always be maxing out and my CPU hovering near 90C when web browsing... going to suck when I actually want to do something with it.

    At this stage do I need to consider contacting Apple?
  9. Mekker macrumors newbie

    Aug 11, 2012
    After i updated my Macbook Air 2012 today with the new update to improve graphics. I got the same problem, the CPU is very hot after a restart for no resaon and it drops slowly in temp after loading up OSX.

    Normally I would be around 40-60c, after restart i'm between 80-90c and it then drops to normally temps.

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