Continuous fans harmful to 24" iMac?

Discussion in 'iMac' started by dogbane, Mar 16, 2009.

  1. dogbane macrumors newbie

    Feb 12, 2008
    My aluminum 2.8 Ghz iMac's three fans have been running continuously for about a week now. I've tried shutting it down overnight and resetting the SMU myself, but nothing even slows them down. The moment I turn it back on, they all start up. It's not running hot at all, no more than 41 celsius even when a lot of apps are running. Any ideas on how to fix this?

    But my main question is, will this hurt anything? Fans used to run continuously on computers without "burning out" or going bad or failing or anything. It's going to be incredibly inconvenient for me to get this to an Apple dealer, so I'm considering just putting up with the noise for a while. Any harm in that?

  2. Hellhammer Moderator


    Staff Member

    Dec 10, 2008
    Have you tried SmcFanControl? Download it from here

    It allows you to change the fan speeds
  3. dogbane thread starter macrumors newbie

    Feb 12, 2008
    I should have mentioned this originally; I have tried it. It's good for setting the minimum fan speeds, which isn't my problem. I made sure my fan speeds are set to the minimum, but beyond that I didn't see any way for this software to help. Or am I missing something?

    The Fans widget shows one of the fans (the one on the right) going way over the minimum, at 3.2K, by the way. I don't know if that's significant.
  4. synagence macrumors 6502a

    Jul 23, 2008
    Its either a malfunction on the heat sensors / controller or there is genuine excess heat building up

    In most of my computers i unload a can of compressed air through (outside) to clear out dust and crap from the fans and heatsinks

    Can you get some monitoring software to show you the actual board/cpu temps to see if they're high
  5. dogbane thread starter macrumors newbie

    Feb 12, 2008
    OK, I've got some of that software installed. The highest temp is in Hard Drive Bay 1, at 58 Celsius. SMART Disc WDC is at 55 degrees, the rest are in the 40s or lower. No problems with those readings, right?
  6. DannySmurf macrumors 6502a

    Jul 7, 2005
    Something else to consider: has the machine been knocked or banged at all? On some models, if the fans become unplugged from the logic board, they will spin up to full speed by default.
  7. dogbane thread starter macrumors newbie

    Feb 12, 2008
    It hasn't gotten banged around that I know of.

    But as to my second question: is this fan activity hurting anything? If I can put up with the noise, can I safely ignore it?
  8. edgew8 macrumors regular


    Dec 8, 2008
    OMG people! the iMac is not a netbook, let the fans run!!! It needs to stay cool!!! If you want your iMac to go to 50c while idle, go ahead, its your iMac but personally I think its a terrible idea. Just let the cooling fans do their job IMO.

    Also 58c for the Hard drive bay is a little hot. I almost wonder if the fans are revving up to get that temp down...
  9. dogbane thread starter macrumors newbie

    Feb 12, 2008
    I'm happy to let my fans do their thing. They cooled well and unobtrusively for seven months, unheard, until about a week ago. Now all three run continuously and loudly from the moment the machine is turned on. That's not normal.
  10. edgew8 macrumors regular


    Dec 8, 2008
    you may have a faulty/loose temp sensor. Like I posted earlier, your hard drive is reading pretty hot @ 58c and that is not normal and may be cranking your fans. You should go to an Apple store and have the iMac checked. I wish I could help you more but I would have to open the machine up to properly diagnose it.
  11. dogbane thread starter macrumors newbie

    Feb 12, 2008
    Thanks, that's good to know. If there is a genuine problem the fans are trying to solve, I'll want that looked at. I'll take it in tomorrow. Thanks to everyone for your help.
  12. dogbane thread starter macrumors newbie

    Feb 12, 2008
    ...though, come to think of it, that still wouldn't explain why the blasted fans start blowing immediately upon startup, even after the machine has been off and unplugged all night. We'll see what the techs say.

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