iMac 27" fan speeds

Discussion in 'iMac' started by G-Force, Jun 12, 2010.

  1. G-Force macrumors 6502a

    Nov 25, 2006
    Hi all,

    I have a new iMac 27" and I'm starting to think my CPU fan speed is a bit too high sometimes. When I start up the computer it usually runs at 950-1100 RPM which is nice and quiet, but as soon as I start doing simple things as read my mail and browse the internet the fan revs up to at least 1300-1400 RPM which can be heard. Sometimes out of nowhere it will rotate even faster, for example it currently runs at 1653 RPM which is annoying because the computer is not quiet now. The CPU usage is around 0-3% right now. Sometimes it will slow down again to 1300, but that usually takes a VERY long time.

    This is the second 27" iMac I own because the first one was defective, but I can't remember the first one making as much noise as this one. I've reset the SMC and PRAM several times and it doesn't make it any better. Also, I've reinstalled Mac OS X and that also didn't help.

    On a side note, my wireless Apple keyboard is constantly waking up the computer from sleep. This can't be normal right?

    So my question to other i7 owners, how does your CPU fan behave after a few hours of simple use and does your BT keyboard wakeup your iMac without you touching it?

    Thanks :)
  2. rnb2 macrumors regular

    Jan 23, 2006
    West Haven, CT, USA
    How cool is the room you're working in? I'm in a 3rd floor apartment, and as the weather has gotten warmer (ambient in the high-70s F), my CPU fan has been running at ~2000rpm most of the time. However, my environment is not quiet - I have three external hard drives with fans (including a Drobo, which can get quite loud), and a turtle tank with two filters that are fairly noisy, so I never hear the fans in my iMac (except at night, when the turtle tank goes quiet).

    In fact, I'd rather have the computer make a little bit of noise (given my environment) than run too hot, so I've used iStat Menus to crank all of the fans up and keep everything cooler.

    I do know that something wakes my iMac up from sleep, but I don't know what it is - will have to check on the keyboard issue. How did you establish that it was the keyboard that was waking yours?
  3. TMRaven macrumors 68020


    Nov 5, 2009
    You should always give temps along with fan speeds :)

    Having "wake for network access" under power saver can sometimes wake the computer, but it should go back to sleep on its own. Sometimes, bluetooth keyboard and mouse can wake the computer as well, when their batteries are low-- this is rather random, as the popup windows giving the low battery life are random as well.
  4. G-Force thread starter macrumors 6502a

    Nov 25, 2006
    It has been a little bit warmer on my room these days, maybe that's the cause. The strange thing is, if I shut down my Mac and turn it on directly after turning it off it runs very quiet (950-1150 rpm), but eventually it will rev up again to 1600 and never come down again.

    About the keyboard waking up my Mac, I saw some references to Bluetooth waking up the Mac and the only BT device I use is my keyboard.

    Will post temps later, I'm in Windows 7 right now. Another strange thing is that the iMac is whisper quiet now in Windows 7.

    It's cool in my room now.

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