20" imac making loud humming sound and shutting off while watching DVDs

Discussion in 'iMac' started by nursingstudent3, Jun 19, 2010.

  1. nursingstudent3 macrumors newbie

    Joined:
    Jun 19, 2010
    #1
    I have a 20" imac that recently started making a loud humming sound (sounds like a fan). It starts when I first turn the computer on and is almost consistent. There may be very short pauses but for the most part it is always humming. It has completely shut itself off while I was watching a DVD two or three times. I have also noticed that when I manually shut it off it does not show the screen with the one minutes count down. It just turns right off, I am not sure if that is related. Also when I power it on it sometimes takes pressing the button multiple times. All these different "odd behaviors" started after it made this humming sound. This is the first time I have been on a forum and all of you know more about computers than I do. Please and advice or diagnosis would be greatly appreciated. Also when I put it in sleep mode it has made the humming sound. PLEASE HELP
     
  2. Sun Baked macrumors G5

    Sun Baked

    Joined:
    May 19, 2002
    #2
    Stick the first System Restore DVD in and restart and hold down the D key to run Apple Hardware Test, this should help pinpoint which sensor or part of the machine is causing problems.

    ---

    Lacking that, the logs may show what is causing it to shut down, should be an error from the item that the fan is speeding up for.
     
  3. nursingstudent3 thread starter macrumors newbie

    Joined:
    Jun 19, 2010
    #3
    Thanks Sun Baked. I ran it once and it found an error and gave me a code. The instructions to the left say to "disconnect peripherals attached", is this referring to copiers or printers that are attached to the computer? I ran it a second time as instructed with the printer disconnected and I was given a second different code. What do I do with those codes? In the last message you said that the logs may show what is causing it to shut down. Where does it show the logs at? Thanks again.
     
  4. Sun Baked macrumors G5

    Sun Baked

    Joined:
    May 19, 2002
  5. nursingstudent3 thread starter macrumors newbie

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    Jun 19, 2010
  6. Sun Baked macrumors G5

    Sun Baked

    Joined:
    May 19, 2002
    #6
    4MOT/1/40000002:ODD
    Optical drive blower/ fan
    Verify that the ODD blower/fan cable is securely connected to the MLB and that there are no obstructions that would prevent
    the blower/fan from rotating. Replace the optical blower/fan if the error continues.

    4MOT/1/40000002:HDD
    Hard drive blower/fan
    Verify that the hard drive blower/fan cable is securely connected to the MLB and that there are no obstructions that would prevent the blower/fan from rotating. Replace the hard drive blower/fan if the error continues.

    4MOT/1/40000002:CPU
    CPU blower/fan
    Verify that the CPU blower/fan cable is securely connected to the lower left corner on the MLB and that there are no obstructions
    that would prevent the blower/fan from rotating. Replace the CPU blower/fan if the error continues.
     
  7. nursingstudent3 thread starter macrumors newbie

    Joined:
    Jun 19, 2010
    #7
    Thank you so much, you are very, very informative. My error is the 4MOT/1/40000002:HDD
    Hard drive blower/fan
    Your instructions are "greek" to me. Is this something I should not attempt myself or is this a fairly easy thing to assess? I have never taken a computer apart.


    Also when I disconnected the printer and ran the test a second time I got this error 4MOT/3/40000004:HDD I searched online but could not find this particular error code, any idea what this one is?

    Thank you again Sun Baked for all your helpful knowledge
     
  8. Sun Baked macrumors G5

    Sun Baked

    Joined:
    May 19, 2002
    #8
    Can look at iFixit to see how hard it is, but if you have to take the machine apart to get to the fan -- might as well update the HDD at the same time.

    http://www.ifixit.com/Guide/Repair/Installing-iMac-Intel-20-Inch-EMC-2266-Hard-Drive-Fan/933/1

    Of course you won't know if the fan is dead or dust is causing it to slow down and cause an error, since I think people have said the computer expects a certain fan speed depending on the fan energy input ... don't get it due to dust or fan dying and it'll error.
     
  9. nursingstudent3 thread starter macrumors newbie

    Joined:
    Jun 19, 2010
    #9
    Thanks again SB. I checked out the site and it looks pretty intense so Ill probably just send it in. Thanks very much for walking me through all this. Take care
     

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