iMac fan goes crazy

Discussion in 'iMac' started by rogersmj, Jan 20, 2007.

  1. rogersmj macrumors 68020


    Sep 10, 2006
    Indianapolis, IN
    Three times now, over the last two months (at least three times that I've been around to notice it), my iMac's fan has suddenly spun up from near-silent to full-blast-I'm-about-to-take-off-from-your-desk. It then gradually (VERY gradually) winds down to normal, near-silent speeds again over the course of about a minute and a half.

    I've got iStat, and there's only minimal CPU usage and there's no temp spikes when this happens. This time I was just browsing the web; last time it happened, I wasn't even using the computer. Any ideas to fix this? Anyone else have this happen?
  2. VanNess macrumors 6502a


    Mar 31, 2005
  3. jimbama macrumors newbie

    Oct 5, 2006
    Same thing happened to me for the first time last night. Incredibly loud and sudden- scared the crap out of me. If it happens again I'll call applecare, please post any other experiences here as well....
  4. Maynerd macrumors regular

    Jan 4, 2007
    The first day I got my imac about 12 days ago now after a few hours of use I left my computer. I returned a while later and when I was about to sit down my imac made the noise you are describing it was a loud fan noise. It was crazy loud. I thought it was weird. I have never heard it do that again since though. Not sure what caused it or why it would do that only never to do again but it was weird for sure.
  5. Cybergypsy macrumors 68040


    May 16, 2006
    Central Florida!
  6. rogersmj thread starter macrumors 68020


    Sep 10, 2006
    Indianapolis, IN
    Well, thanks for the tip about the SMC reset, but I basically did that when I moved three weeks ago and it's done it once since then.

    I don't really care that much I guess, since the thing is dead silent most of the time. Like I said, this has only happened three times in months. As long as it's that rare, I'm not going to bother handing it over to Apple. Maybe a firmware update in the future will fix it.
  7. 2Shae macrumors 6502

    Sep 7, 2006
    I just had it a couple of minutes ago! Out of nowhere.
    And it scared the crap out of me, I thought it was gonna blow up in my face or something:p

    Do you also have a 20" iMac intel Core 2 Duo (with upgraded Ram & Graphics card) ?
  8. Edwin the Elder macrumors member

    May 4, 2005
    Ottawa, Canada
    I am having problems as well

    I have tried resetting the SMU but I am still having 2 problems on my G5 iMac over the past couple of weeks:

    1.when the iMac goes into sleep mode (either because I put it in sleep mode or due to inactiviy) it shuts down after awhile. The power button stops pulsing and the machine is off. I can restart it normally. This happens all the time now.
    2. On occasion, after the computer has gone into "sleep mode" the fan gets really loud. Apart from the fan noise, the iMac appears to be off - the power button is off, teh screen is balnk and the computer does not respond. Hitting the power button does absolutely nothing. It doesn't turn the fan off, it doesn't start the computer. I have to turn the power off at the power bar. That stops the fan and allows me to power the computer back up.

    I could be wrong, but it seems like I've been having these problems since I downloaded the latest software update.

  9. queshy macrumors 68040


    Apr 2, 2005
    Sorry, can't really help you there. It does sound like it is a problem that really should be adressed. Good luck!

    As for the poster, that fan thing is definitely not normal. There was a point where my PC did the same thing for an unknown reason, but I formatted it and it hasnt' done it since. Not sure if that even fixed don't quote me! Good luck to you as well.
  10. Mr Skills macrumors 6502a

    Mr Skills

    Nov 21, 2005
    Oh. I read the thread title and I was imagining someone running around hysterically going "wwaaaaahhhh! I love iMacs!" :p
  11. sushi Moderator emeritus


    Jul 19, 2002
    For those with loud iMac fan sounds, have you installed the latest Firmware and SMC updates?
  12. ninewhereman macrumors member

    Jan 8, 2007
    Haha +1 I was slightly disappointed.
  13. rogersmj thread starter macrumors 68020


    Sep 10, 2006
    Indianapolis, IN
    FWIW, it hasn't happened to me since I originally created this thread. I do always stay current with software and firmware updates.

    I have that iMac (see sig), but not the upgraded graphics.
  14. mainemacuser macrumors newbie

    Mar 6, 2007
    iMac fan goes crazy

    The flat panel iMacs just prior to the intel iMacs had a similar problems which turned out to be a Power Supply problem. My sister had to have the power supply replaced along with the motherboard. It worked great after that, but it was a struggle to get the problem diagnosed. The first sign though was the fan would seemingly spin out of control. Good luck!
  15. sushi Moderator emeritus


    Jul 19, 2002
    Most interesting. Thanks!
  16. Mydel macrumors 6502a


    Apr 8, 2006
    Sometimes here mostly there
    My iMac G5 with isight does that every so often. It maybe happened 10 times in last 16 months or so. I also have no idea what is that. I remeber calling apple about that but they weren't any help, and cos this iMac is at my gf house in Poland I just asummed that as long as works Im not gonna be shipping it back to US just to take it to aplle store. Especially that its really rare...
  17. discoforce macrumors 6502a


    Jan 27, 2004
    Vermont, USA
    I've experienced the same whooosh from my iMac fan twice now, and I'm running the latest firmware updates.
  18. Dagless macrumors Core


    Jan 18, 2005
    Fighting to stay in the EU
    Well this thread is more bustling than mine so-

    I had this happen to me last night. I've spent more time under XP since Christmas (big uni project, PC app only etc) and it happened in the short window that I used OSX for last night. Latest f/w and everything. Not hot, no huge applications running...
    The mystery continues.
  19. cherub macrumors newbie

    May 17, 2008
    resetting the SMC worked for me

    iMAC 7.1 with Intel core duo SMC version 21f4
    went crazy with fan spinning like a windmill after just standard power on.
    No improvement after multiple shutdown and restart. :eek:

    I was able to fix it thanks to VanNess and his link

    I suspect this is related to my recent practice of turning off power at night to the power string where my iMAC and other peripherals are attached. :confused:

    I understand now this practice is equivalent to reset SMC every night.
  20. wexford macrumors member

    Nov 30, 2007
    i've had this happen twice on my white imac 2.16ghz.

    i think it might have something to do with java.
  21. ajohnson253 macrumors 68000


    Jun 16, 2008
    hahaha im just picturin someone sitting there and then they hear some loud random noise, the reaction hahah
  22. lilshortjordan macrumors newbie

    Feb 1, 2008
    Ahha! You just made my day!!!

    My iMac has done this maybe 5 times in the last 3 days, I don't know what I'm supposed to do, its driving me crazy
  23. GugGog macrumors newbie

    Dec 11, 2009
    I had an I7 that sped up from silence to a "wind turbine" noise with zero programs running, and nothing taxing the CPU. It took around 30 minutes and gradually kicked in.

    I replaced the set up with an I5 plus a "regular" 27" iMac combo (dual monitors), and both are completely silent, no matter what I throw at them. I can literally hear road noise outside my double-glazed windows -- there's nothing to suggest the Macs are on except for the screens!

    My (completely amateur) advice? I was told the "fan noise" issue was a sensor problem. But that's MY distinct issue rather than the fan suddenly roaring. I installed istat to check RPMs, and my CPU fan was rocking at 6500+ (apparently normal operating levels are around 1000).

    Get the unit replaced or repaired if you can't live with the noise, I reckon.

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