iMac Fan Speeds

Discussion in 'iMac' started by, Oct 28, 2007.

  1. macrumors newbie

    Oct 28, 2007
    Hi all,

    I recently bought my first iMac (2.0GHz) and love it. It's a great computer and Mac OS X is very user friendly.

    I have however some concerns about the fan noise. According to some user entries here, the iMac is supposed to be absolutely silent but I can here some fan noise.

    Can you please post your fan speeds so that I can compare them with mine?

    Mine are:
    - Optical Drive: 998rpm
    - CPU Fan: 1199rpm
    - Hard Drive: 1199rpm

    Many thanks,
  2. Washac macrumors 68020


    Jul 2, 2006

    Mines quiet...

    What noise you hearing ?
  3. epmatsw macrumors member

    Jun 18, 2007
    Just listening to music and using opera, these are my speeds

    999, 1199, 1267
  4. thread starter macrumors newbie

    Oct 28, 2007
  5. OwlsAndApples macrumors 6502a


    Oct 4, 2006
    I have an older mac (see sig), but it is completely silent to my ears. All i need is to get my £34 upgrade from Crucial and it should run smoother.
  6. thread starter macrumors newbie

    Oct 28, 2007
    It's really weird. The iMac doesn't make any "heavy" noise but there is some kind of summing/humming coming from it. Basically, it's silent but I can hear it when not listening to music.

    I'm not sure if this is normal. It's a a lot quiter than my old computer.

    Any thoughts?

  7. IChing macrumors regular

    Sep 25, 2007
  8. ScottFitz macrumors 6502a

    Nov 3, 2007
    Maybe not rocket science, but fans are cheap parts. If the bearings start to go, you get noise. If it gets bad, take it in and have someone pop a new fan in for you.
  9. airjuggernaut macrumors 6502a

    Oct 16, 2007
    I hear sound coming out of my iMac too.
    It's not too bad, but it's definitely audible.
  10. airjuggernaut macrumors 6502a

    Oct 16, 2007
    Sorry to reply again, but i want to bump up this post to see if this a common problem with the iMac or not.

    I've been reading around and have heard about others experiencing Loud sounds on 20inch iMacs. The fans make a slight hum, but sometimes when launching a program i hear a screech..I think it might be just the Hard Drive reading.
    Not a major Issue, because well the iMac is a computer afterall, but I want to see if other users are experiencing this.
  11. Big-TDI-Guy macrumors 68030


    Jan 11, 2007
    I've noticed differences in "average" fan speeds between my 20" CD and 24" C2D (both white imacs)

    The 20" tends to run faster on all 3 fans.

    My 24" #s CPU: ~900 Hard Drive: ~1100 Optical: ~600

    Now, in warmer weather, they obviously ramp up higher.

    I've noticed that running full CPU brings the speeds up on the CPU and Hard Drive fans - but stressing the GPU seems to kick it up even more. Also, more backlight intensity plays a role in generating more heat. Having the 24" being overpoweringly bright, mine is always at minimum.

    Finally - dust can be a substantial factor, cleaned out a friends intel mac, (had LOADS of dust in it) all 3 fans ran much slower at the same temp / workload. And it was once again near-silent.
  12. gorby macrumors 6502

    Oct 20, 2007
    How do I check my fan speed?

    I've been meaning to ask about noise too....

    Mine is clearly audible, it's not loud, but it's not "silent" either.

    The sound has two components, a sort of 'buzz', and a whirling wind sound (barely audible) which I assume is the fan.

    Being as this is my first mac, I don't really have anything to compare it to (definitely quieter than my old PC) I wonder if you other white mac owners would say my description matches yours.

    If the machine was under the desk I don't think I'd hear anything.
  13. Big-TDI-Guy macrumors 68030


    Jan 11, 2007
    I use the Istat Pro Widget to monitor things. It is free, and works great. Nice dashboard accessory to have. (gives you temps, processes, internet - just about everything)

    The noises: First off, the speed control on the fan will make a distinct hum, due to the pulsing required to maintain it's current speed - just about every brushless motor does this.

    Although on the white 24" Imacs, some had a more audible backlight hum than others. (stemming from the backlight supply) If it changes intensity or pitch when brightening or dimming the display - that's the backlight supply.

    The whirring noise also is likely the fans. (unless you've got a disc cranking away in the optical drive)

    Other vibration can be from the balancing of the fan shaft/impellers, and your hard drive spindle/platter.

    Whenever your hard drive is seeking or writing info, the wiper arm/head will make some noticeable chatter.

    Last off, sometimes the main power supply will whine, usually when the unit is in standby, or shut down. Though - I only heard this on my 20" white imac, the 24 seems fairly quiet.
  14. gorby macrumors 6502

    Oct 20, 2007
    Neat-o! I swear, it's just awesome learning these cool things everyday. Too much fun. Here are my stats:

    optical: 598
    cpu: 999
    harddrive: 1299

    Thanks for that explanation / comparison, TDI Guy.

    Yeah, I did notice the humming as the display is dimmer, but it's not an issue.

    And overall, it's pretty quite too, it's more noticeable if I cock an ear towards it. Love this machine!
  15. dL. macrumors 6502

    Nov 5, 2007
    I have the same fan speeds as you guys, and yes I do hear very minor humming noise when the room is dead silent. Way quieter than my PC down there even though it's very quiet already :p

  16. rainydays macrumors 6502a

    Nov 6, 2006
    Mine is fairly noisy. Not loud, but noisy. Since I've had four of them I know that it's not supposed to be. It seems that it's the CPU and ODD fans that are having problems on mine. It varies over time, sometimes it's at an annoying level, sometimes it doesn't bother me that much, but the fan speed is still the same.

    I noticed that I can lower the noises some if I turn the fan speed up a bit. But the computer gets overall louder at the same time so it's not really a solution. The solution would be to swap out the fans. I just can't be without the computer at the moment since I need it for work. Too bad they won't let me swap them out myself.
  17. airjuggernaut macrumors 6502a

    Oct 16, 2007
    I'm thinking about taking it back to apple store...I'm not sure though..
  18. Big-TDI-Guy macrumors 68030


    Jan 11, 2007
    If speeding up the fans smoothes out the vibration - then the spindle or impellers might be out of balance. If it's under warranty - def. bring it in to be checked out.
  19. thread starter macrumors newbie

    Oct 28, 2007
    Hi all,

    Good to know that I'm not the only one who hears the fans and/or harddisc. Not sure if I should call AppleCare but it's starting to annoy me. It's my first Mac, just 25 days old and I already have some problems with it. I always thought Apple Computers are highest quality...

  20. RRK macrumors 6502


    Mar 14, 2007
    I think you guys should take them in for repair because I have my fans bumped up to 1500, 2500, 1500 and I cannot hear the fans in silence unless I concentrate.
  21. wellmac macrumors member

    Oct 30, 2007
    iMac 24" 2.8

    CPU 1198
    HDD 1198
    Optical 698

    I can just hear the fan. It's not worth worrying about and is sooo much quieter than PC. Yeah I can hear the hard disk too, but it's hardly annoying.

    Cool widget BTW.
  22. terriyaki macrumors 6502a

    Aug 4, 2005
    My 20" 2.4 is ridiculously quiet.

    CPU: 1199rpm
    Hard Drive: 1268rpm
    Optical Drive: 998rpm
  23. vansouza macrumors 68000


    Mar 28, 2006
    West Plains, MO USA Earth
    very quiet

    CPU 1506 rpm
    HDD 1504 rpm
    Opti Drive 1021 rpm

    CPU-a 36 C
    Airport Card 39 C but would be 59-61 if it was on.

    oops... I raised the RPMs with smcFanControl2
  24. wackymacky macrumors 68000


    Sep 20, 2007
    38°39′20″N 27°13′10″W

    There has been occasional users with the new Alu iMacs having faulty temp sensers and hence fan going too quickly.

    Your fan speed apear normal (the above ones run at 3500-4000).

    Despite what the others say as the iMacs have three fans and thus are not silent , just are (very) quiet. It is normal for there to be an occasional soft noise tough this sould be just audiable.
  25. swek macrumors newbie

    Nov 18, 2007
    I have the humming sound going on my alu 20" imac, and seeing as it is constant when i rev up the fans using smcFanControl, it is impossible for it to be coming from the fans. I have instead ruled it out to being the HDD. It spins up nice and slow just like a drive does when i wake the computer from sleep.

    If you listen carefully to your imac as it wakes from sleep, it will rev up the three fans individually, and then drop them down to lower speeds, meanwhile the harddrive will come to life and slowly rev up to its 7200rpm, and the humming comes in place.

    Another weird thing I've noticed is that when I have my Maxtor OneTouchII drive mounted the noise starts to pulsate. This is probably because the drives run att similar speeds, 7200rpm, and there is interference between the two so that the noise is periodically cancelled out.

    The hum from the external drive has the exact same frequency as the hum from the imac.

    I think it's going in for repairs..

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