Fan Noise on Startup and Wake from Sleep

Discussion in 'iMac' started by icemantx, Sep 18, 2013.

  1. icemantx macrumors regular

    Mar 16, 2009
    I have an older iMac (early 2009) and have a question about fan noise. When I start the computer from off, restart or wake from sleep I hear a rather loud whirring sound like the fans spinning up real fast briefly then slowing down to a quiet normal speed.

    Is that normal?

    I ran smcfancontrol to check my fan speeds and temp and the fans pretty much stay constant at CPU:800 and HDD: 1600 with a temp of about 41c.

    The iMac is quiet overall when running but the jet engine like whirring sound that has actually been there since I bought it just had me wondering today.

    Overall the iMac does run fine and there is no other problem with excessive fan speed or noise.

    Thanks for the help!

  2. icemantx thread starter macrumors regular

    Mar 16, 2009
  3. rkaufmann87 macrumors 68000


    Dec 17, 2009
    Folsom, CA
    Reset the SMC and PRAM, do each at least 2 times.
  4. icemantx thread starter macrumors regular

    Mar 16, 2009
    No luck - any other ideas?
  5. Brian33 macrumors 6502a

    Apr 30, 2008
    USA (Virginia)
    It's normal. My 24" Early 2008 iMac does the same thing, and has ever since I bought it (new). I guess I always figured it was just some sort of system check -- "yup, the fans are working" -- kind of thing.

    I've never had any heat or fan problems with my iMac.

    One thing I found rather odd: if you have some sharing services turned on and an Apple Time Capsule or Airport Extreme Base Station, the router will wake up the iMac very briefly every hour (I believe) to refresh its list of bonjour services. The iMac screen doesn't come on, but the fans do -- and it can be rather surprising if you're in a quiet room and don't expect it! But it's normal.
  6. icemantx thread starter macrumors regular

    Mar 16, 2009
    Yeah - that is what I was thinking, but had nothing to compare it to. Good to know it is normal behavior and nothing to worry about.
  7. ElectronGuru macrumors 65816

    Sep 5, 2013
    Oregon, USA
    Yeah, like lights on your car dashboard when you turn the key.

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