My iMac is making a loud fan noise and I can't fix!

Discussion in 'macOS' started by hagop, Mar 25, 2013.

  1. hagop macrumors newbie

    Mar 18, 2013
    My iMac is making lousy loud fan noise every time I turn it on and stays like that for the whole time it's on and I do not know how to fix this issue.

    I have iMac, Mac OS X Lion 10.7.5, 3.06 GHz Intel Core 2 Duo.

    How can I fix this problem?

    Thank you
  2. GGJstudios macrumors Westmere


    May 16, 2008
    First you need to determine if the fan is spinning faster because of increased heat, which is usually an indication of a heavy workload.

    If you're not already doing so, use iStat Pro (free) or iStat Menus ($16) to get accurate readings of your temps, fan speeds, etc., rather than relying on your sense of touch or sound. A forum member has posted a copy of iStat Pro that has been "tweaked" to enhance compatibility with Mountain Lion. You can download it here.

    The Intel processors used in Macs are designed to automatically shut down to prevent damage if they truly overheat. CPU Tjmax = 105C (221F), GPU Tjmax = 100C (212F) on i3, i5, i7 processors. (Source: Intel)

    Unless there is a rare defect in a Mac, most temps are well within the normal operating range, considering the workload being put on it. Websites with Flash content, games and other multimedia apps will put higher demand on the CPU/GPU, generating more heat. This is normal. If you're constantly putting high demands on your system, such as gaming or other multimedia tasks, expect temps to rise and fans to spin up accordingly. It's just your Mac doing its job to maintain temps within the normal range.

    It is also quite normal for your Mac to become extremely hot to the touch during intensive operations. The aluminum body transfers heat more effectively than other materials used in computer casings, so you will feel the heat more. This doesn't indicate that it's overheating and will not harm the computer to be hot to the touch.

    Your fans are always on when your Mac is on, spinning at a minimum of 2000 rpm (for MBPs) or 1800 rpm (for MBAs, MBs and minis). iMacs have 3 fans with minimum speeds in the 800-1200 range. They will spin faster as needed to keep temps at a safe level.

    If your fans are spinning up without increased heat, try resetting the SMC.
    (PRAM/NVRAM has nothing to do with these issues, so resetting it will not help.)

    The intake and exhaust vents are in the back of the computer near the hinge on all Mac notebooks (except the new MBP with retina display, which has intake vents along the sides at the bottom). The iMac vent is a slot on the back near the top of the computer. Make sure the vents remain unblocked to allow your computer to perform at its best.

    Learn about the fans in your Mac
    Apple Portables: Operating temperature

    For Flash-related issues:
  3. hagop thread starter macrumors newbie

    Mar 18, 2013
    The fan is spinning up without increased heat so I did the SMC reset, but nothing has changed.

    I do not put too much workload on my Mac, all I do is work on my Google Chrome with couple of websites open & my emails.

    I did Install iStat Pro and it shows the following indications:
    Temps(in Celsius): HD: Mac HD 33
    CPU 34
    Ambient 18
    GPU Diode 41
    GPU Heatsink 39
    Men Controller 40
    Northbridge 49
    Optical Drive 34

    Fans: Optical Drive 999rpm
    Hard Drive 5202 rpm
    CPU Fan 939 rpm
  4. GGJstudios macrumors Westmere


    May 16, 2008
    It appears you may have a defective hard drive sensor or fan. Take it to Apple and they can diagnose the problem for you.
  5. hagop thread starter macrumors newbie

    Mar 18, 2013
  6. lucadgoalie macrumors newbie

    Jun 5, 2014
  7. satcomer macrumors 603


    Feb 19, 2008
    The Finger Lakes Region
    I bet your iMac is full of dust! Do a search for local tech service that will take the iMac apart to clean it out. You also could replace/upgrade/add a second drive at the same time.
  8. panakjimtech macrumors newbie

    Aug 13, 2014
    I had then same problem. I tried to switch off and on, nothing helped for 3 days. Then I removed the power cord and then restarted the computer. That stopped the fan.
  9. jbos macrumors newbie


    Jan 11, 2017
    Hi there!
    Reviving the problem on an imac24 2008 with ElCapitan...

    Resetting SMC & NVRAM and nothing has changed.
    After a short period of booting, the fan is starting to increase speed until it reaches the full speed!

    with macs fan control i have these results:
    Region capture 8.png
    CPU fan works at full speed...
    Its possible to decrease speed but... is it ok?

    I tried to customize speed in relation to GPUdiode temp and decreases as follows:
    Region capture 7.png

    do u think that is ok?

    Is it only acoustical my problem or not?
  10. Nickxyz macrumors newbie


    Feb 3, 2017
    I just had this problem (loud fan not due to overheating), 2009 vintage iMac, restarting didn't help so I turned it off, vacuumed the dust out of the vent, turned it back on (removing the power cord so apparently that's resetting the SMC) - and then beautiful silence.
  11. jbos macrumors newbie


    Jan 11, 2017
    i changed the graphic card with a reballed one to resolve the problem.

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