new imac 21.5 heat and faint noise issue

Discussion in 'iMac' started by msregister, Aug 29, 2010.

  1. msregister macrumors member

    Nov 6, 2008
    received my new imac 21.5 and was wondering if there is a problem with this unit.

    1. the top back feels extremely hot, you cant keep your fingers there for more than a 5 seconds.

    2. when touching the top back i feel a slight vibration and there is always a faint buzzing sound present. my previous imacs were dead quite.

    the istat nr. with moderate use are:
    Ambient 28
    CPU 60
    GPU Diode 67
    GPU Heatsink 66
    Mem Controller 61
    Optical Drive 50
    Power Supply 74
    Hard Drive 54
    CPU Fans 1806
    HD 1549
    Optical 1172

    please let me know if all this is normal or there might be an issue with this unit.

    thank you in advance.
  2. stridemat Moderator


    Staff Member

    Apr 2, 2008
    It doesn't seem out of the ordinary. Due to the material of the new iMac's they do have the tendency to act as a heatsink. If the vibration is worrying you then perhaps try a replacement unit.
  3. SiMBa37 macrumors regular

    Jul 5, 2010
    New York
    I have a 21.5" as well, it does get very warm on the top but ive never measured the internal temps. My mac is whisper quiet.
  4. mrfoof82 macrumors 6502a

    May 26, 2010
    Lawton, OK
    Temperatures are normal.

    However the general recommendation on most Macs is to raise the minimum CPU fan speed from 1800rpm to 2300rpm. That'll reduce those 60-65C temps to more around 50C. The computer will also still be inaudible at 3 feet.

    Use the Fan Control preference pane plugin, or SMC Fan Control to change the minimum speeds and set the ramp-up thresholds.
  5. Spike88 macrumors 6502a

    Jan 25, 2010
    I agree. Since OP's iMac has Ambient 28 (which to me is high), I would use 3rd party Fan Control software to add more internal cooling. Thus, proactively lowering those higher temps (from a proactive approach).

    If wondering, my 21.5" iMac temp stats are:

  6. msregister thread starter macrumors member

    Nov 6, 2008
    appreciate the responses.

    if as some suggest that i should raise the fans then my question is whether this is a "faulty" unit and that i should ask apple to exchange it?
  7. pt0016 macrumors regular


    Jul 9, 2010
    Not faulty.

    The fans are higher than idle, showing that the computer acknowledges that it is running warmer, and is cooling the computer down. The graphics card at 67degrees and CPU at 60degrees is perfectly normal, the maximum temps of your machine are way higher than what it is running at, stop worrying.

    The temps of the poster above me seem to be abnormally cool - you must have just turned the computer on, or you live in a freezer, in the winter here in New Zealand, my iMac idles at 37degrees CPU and 50degrees GPU.
  8. msregister thread starter macrumors member

    Nov 6, 2008
    thank you,

    is the faint noise / buzz something to be concerned about?

    it does not sound like a fan, its more like a spinning sound. all my previous imacs were dead quite.
  9. stridemat Moderator


    Staff Member

    Apr 2, 2008
    Only if it's loud would I worry about it. Monitor it and if it gets worse then think about taking it to see a Genius.
  10. Spike88 macrumors 6502a

    Jan 25, 2010
    No. I don't live in a freezer. Here's today's screen captures - of my iMac 21.5" fan speed settings and its internal heat temps. If wondering, typical home email/file/print user. And, my iMac system is on 24/7 (connected to UPS unit). Only rebooted for Apple Updates - like today's 2 x updates. Other then that, nothing too wild....



    As seen, Ambient is now 23C. Typical temp in my basement office.

  11. Elyquin macrumors member

    Aug 24, 2010
    How close are you putting your ears?

    We got our iMac a week ago. If I put my ear next to the machine, then I can hear fan noise and some humming.

    From a normal distance to the monitor, the machine is very quiet. The loudest noise is from the ceiling fan (medium fan) or from the external hard drives.
  12. aki macrumors 6502a

    Mar 2, 2004
    There are lots of very informative threads on this topic. Here is my considered view for what it's worth.

    Firstly, iMacs do run on the hot side. They are pretty cramped (yes even the 27") and designed to be svelte. That has a cost.

    Second, they get hot to the touch. This is most certainly by design. Touching your iMac tells you nothing except that the heat dissipation is working well. If you want to know what's going on inside, which is the point, use iStat or similar.

    Third, for normal use, the iMac does not require user intervention. This begs the question "What is normal use"? Here's my take. If you upgrade your hardware regularly, don't worry about temps. If you want or may want your iMac to last into the 3 to 5 year range, you should give it a thought. If you use your iMac mostly for email and websurfing and writing papers, forget about temps. If you do marathon gaming sessions, if you often game in bootcamp Windows, or if you do video processing or other "heavy lifting", you should give temps some thought.

    Fourth, most people who worry about temperatures worry about them needlessly; see point three above.

    Fifth, if you do use your iMac for heavy work or often use Windows and do want your machine to last a bit longer or at least know what's going on, the current prefered solution (imo) is iStat or Temperature Monitor or similar, which will give you temps in the menubar or in the Dashboard (OSX side only), and smcfancontrol, which will let you manually set minimum fan speeds (the setting can only be done from OSX, although you can have the fan speed settings carry over to a bootcamp Windows session provided you do a restart and don't switch off the iMac).

    Sixth, if you are setting fan speeds and looking at temps, what should you be looking for? The GPU and CPU are precious and expensive to replace obviously but they are also rated for quite high temperatures. The iMac is designed to shut itself down before you get to that point. What is rather more fragile is your internal HD. High temperatures don't kill HDs immediately, but they do reduce lifespan/increase failure rates. Of course you should be timemachining or similar anyway; but replacing a HD is tedious and stressful and can be very inconvenient. Again, having given due consideration to the points above, I think it's good to set speeds to keep your HD temps in the low 50s C. Under 50C is fine, over 55C is bad, in between is, well, reasonable given what the iMac is. (I should note when I talk about temperatures here I'm talking about high temperatures suistained over a period of time. Spikes in temperature, when you are transcoding a youtube clip or something, that's not worth being concerned about. I'm thinking here about all-night Crysis sessions or whatever.)

    Seventh, and final point. Environmental conditions play a role (more than I originally thought). Depending on where you live, ambient temperatures will have an effect - I'm in Japan and temps are clearly higher in summer than winter inside the iMac. Also, if you live in a dusty environment, it's not a waste of time to dust around your machine and desk regularly - your fans will suck up that dust over time.

    Eighth and actually final point. External fan solutions sound better than they may actually be. I'm not an engineer of any description, but I have read authoritative-sounding accounts of how the fans in the iMac are carefully and cunningly placed so as to maximize efficiency, by directing airflows from certain areas to other certain areas over so and so components. Which is to say, it's all a pretty neatly designed system. There used to be mods around where people would carve holes in the backs of their G5s (this is in the plastic era), and electrical-tape fans on there or what have you. Bad idea (generally speaking) - it just messes with the airflows that some team of very clever Apple engineers burnt countless nights laboring over. Or something. I'm being verbose, the point is, placing little desk fans at the base of your machine or pointing your fan at the air vent in the back might look like its helping - hey, it's cool air, right? - but it may or may not actually be that simple.

    Ok I'm done. Good luck! :)

    PS Ok I lied about being done - if you do elect to use smcfancontrol, it's generally better to trying uping all three fans a small amount than one fan a lot. Again, they are designed to work in concert.

    Update: iStat Menus versions 3 and above (no longer, alas, a free product) allow you to manage fans similarly to smcfancontrol, along with monitoring a billion other things. Its settings carry over to bootcamp sessions like smcfancontrol does. However, iStat Menus displayed some odd behavior on my machine, so I reverted to smcfc.
  13. Danxqz macrumors newbie

    Aug 10, 2010
    I don't disagree with any of those points, but want to raise a query on the issue of external fans and dust.

    I found a nifty little fan at Walmart for $6. 3.5" aluminum fan in a metal case. I removed the fan guard for extra efficiency. I place them as spot cooling fans for my chest or whatever.

    I certainly agree it would be a mistake to alter the internal cooling flow with holes or fans blowing directly into vents. But I don't see a problem with aiming a small cooling fan at the back of the imac's Al case to aid in its dissipation of heat.

    Keeping the area dust free is a good idea, but there is always dust in the room. I assume increasing the internal fan speeds, in addition to cooling the mac, increases the amount of dust flow thru the computer, thus increasing dust accumulation. Perhaps that is an additional reason the default minimum speeds are low, not just for quiet.

Share This Page