iMac C2D -- Which fan is "Fan 2"?

Discussion in 'iMac' started by maverick18x, Feb 1, 2007.

  1. maverick18x macrumors member

    May 31, 2005
    Hey everyone,

    My family got a nice 20" C2D iMac this past christmas. It normally runs whisper quiet, but today there was some loud fan noise. I wasn't doing anything processor intensive, and the iMac is in a pretty cold Minnesota basement... it kinda surprised me.

    I quick pulled up the iStat nano widget and found that "Fan 2" was running at 3500 rpm for a few seconds. Does anyone know which fan "Fan 2" is -- as in where it is located? I'm more curious than I am concerned.

  2. Zwhaler macrumors 604


    Jun 10, 2006
    Can't help you with where the fans are, but on average my fans are usually at 800-1400 Rpms, so 3500 is quite high
  3. maverick18x thread starter macrumors member

    May 31, 2005
    Yep, that's where mine normally are too... this sounded a bit more along the lines of a jet engine, but only for a few seconds. Weird.
  4. Zwhaler macrumors 604


    Jun 10, 2006
    Has it been acting up? Like weird software issues or anything? Or was it just a random burst of fan-age? Because if nothing is wrong with the computer, I wouldn't worry about it. My computer does the same thing right when I start it up (lasts for about half a second) but thats kinda different.
  5. jimbama macrumors newbie

    Oct 5, 2006
    There is another thread on here somewhere where someone was asking about this- seems to be happening to a few people at least. Has only happened to me once but jet engine is a good description....
  6. maverick18x thread starter macrumors member

    May 31, 2005
    Nope, just a one time occurrence. Like I said, I'm more curious than I am concerned.
  7. maverick18x thread starter macrumors member

    May 31, 2005
    Yah, that's a pretty accurate description of my experience too...
  8. nateDEEZY macrumors 6502a

    Jan 24, 2007
    San Francisco, CA
    There are 3 fans in my 24" iMac, one for the gpu one for the cpu and one for the hd.

    The lowest running one is the hd, the highest should be the cpu's and then the mid range one is the gpu.
  9. simon.c macrumors newbie

    Feb 2, 2007
    Fan numbers, speeds and noise

    Been concerned that my iMac C2D 20 inch has got noisier since I got it last month. Putting my head close to the screen I can hear a faint hum. Some people have said this is to do with the screen brightness but not in my case. At the back it is really noticable and like my old PC. I've wondered about the firmware upgrade I did or possibly some sort of hardware problem developing. So I loaded smc Fan Control and iStat Pro desktop widget. By using SMC to increase fan speeds and looking at iStat I found the following:

    Fan 0 ODD 800-5000 rpm (min and max)
    Fan 1 HDD 1400-5000 rpm
    Fan 2 CPU 800-3600 rpm (exhaust vent just above power cord)

    Normal operation is F0 800, F1 1400, F2 800. Turning up the fans gave that fasten your seatbelt feeling, The CPU is the nastiest noise but clearly a fan, nothing sinister. Anyone else got some figures to compare?

    When I first got my iMac I was stunned by its quietness. I could actually hear hard drive seeks and got panicky about that until I realised I had a Western Digital hard drive (not a Seagate - previous bad experience).

    I think for me the noise has not changed I am just getting really picky. Once the initial WOW wears off you listen out more. A real problem is always obvious and it sounds like some people have real problems. The rest is just worry. Its quieter than my Toshiba Portege and I hope it stays that way!
  10. r-sparks macrumors 6502


    Dec 1, 2006
    I've got a 20in 2.16GHz Core 2 Duo system that I bought in Dec 06. One thing I would NEVER describe it as is whisper quiet. :( I wish it were that way, and I'm always astounded when people say that.

    I work in a very quiet home office. I can definitely hear the fans and also the hard disk. The whole system is quieter than virtually every other computer I've owned (apart from notebooks), but it's not silent. Right now I can hear the fans and the hard disk pretty clearly, and I'm just sitting at my desk. It's a slightly annoying, laboring-type noise.

    My fan speeds are 831 (fan 2), 1398 (fan 1) and 797 (fan 0), according to iStat. Note that iStat might not yet be tuned for 20in iMacs C2D, although I understand they recently added support for 24in C2D iMacs.
  11. simon.c macrumors newbie

    Feb 2, 2007
    EFI Update increases minimum fan speed

    I have read that the EFI firmware update that gets downloaded when doing a software update actually increases the minimum fan speeds. This might explain a few things. Apparently MB and MBP owners were literally roasting their nuts. That said my IMAC C2D temperatures are barely worth hospital admission for a human let alone a computer and I would like to go back to the slower fan speed and a quieter life. Anyone know how reduce the minimum fan speed in OS X as no downloadable application will?
  12. Macmadant macrumors 6502a

    Jun 4, 2005
    you say for a few seconds, mine does this when waking from sleep, but all imacs do it
  13. Geekomak macrumors newbie

    Sep 26, 2007
    20" iMAC FAN2 speed jump

    Mine just did the FAN2 speed jump last night. First time ever!! Wierd. I was just surfing the internet, nothing else. Comp was on for about 1/2 hour. I heard a sound like a jet. Then I checked my fan speed and FAN2 was at 2869rpm!! This has never happened before. I've had my iMAC since Feb 2006. The FAN2 speed returned to 800-900 rpm after about 6-9 seconds. I checked with the Apple Site and reset my SMC control. Seems to be hovering around 806 rpm now. I wonder id FAN2 got stuck? Then, jumped in speed?

    Running with osx 10.4.10
  14. wexford macrumors member

    Nov 30, 2007
    same thing just happened to me. white 20" 2.16 imac. sounded like a jet engine for 5-6 seconds, CPU fan was up around 2,600rpm. backed down slowly and returned to normal. like everyone else, i wasnt doing anything intensive.

    any clue yet as to why that happened?
  15. Scorch07 macrumors 6502

    Dec 16, 2007
    Hmmm... I have an old 17" (I don't know if you meant an older white one or a new aluminum one) but iStat does not list a "Fan 2." Either way, my highest fan right now is only running at 1200 RPM so yeah, 3500 is way high.
  16. bluedoggiant macrumors 68030


    Jul 13, 2007
    MD & ATL,GA
    The Aluminum iMacs don't have fans for the GPU!!! I guess its already taken care of or something, but there is one fan for the Optical, HD, and CPU, but no GPU, apple should have included one, I don't think the optical needs cooling

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