iMac G5 Overheating

Discussion in 'PowerPC Macs' started by ercj95, Apr 3, 2010.

  1. ercj95 macrumors newbie

    Nov 22, 2008
    United States of America
    I have an iMac G5 that is starting up, then working okay for 1-2 minutes. After that, the processor usage goes way up, and the fans start spinning loudly. It's a first generation 1.8 GHz with a 17" display. Mac OS X Leopard. Recently, it spun up and then shut down and wouldn't start again. The room it's in is < 75 degrees F. No malodor, or other symptoms save for hot to the touch. Has been left shut off and unplugged for a few hours, and still has this problem. Any help would be greatly appreciated. Thanks!
  2. OrangeSVTguy macrumors 601


    Sep 16, 2007
    Northeastern Ohio
    Use a can of compressed air to blow out the the dust that's blocking the airflow. Without that airflow, the G5 will just overheat and shut down since they are hot processors. An air compressor will do wonders if you have that but be careful not to over-rev the system fans as that could damage them if blowing too much air into it.

    You could also take it apart if you are handy to do a better job cleaning it out.
  3. ercj95 thread starter macrumors newbie

    Nov 22, 2008
    United States of America
    Questioning if it's an overheating issue

    I really appreciate the response, but I'm beginning to question whether or not it is an overheating issue. I've cleaned out all the dust, not a speck remains. Here is some new information you should know:

    - it boots fine from another computer via FireWire Target Disk Mode
    - it boots fine from the Leopard installation DVD
    - it boots fine from the Tiger installation DVD
    - it turns on and gets stuck at the gray screen with an Apple, no loading spinner
    - it is missing the hard drive caddy with the thermal sensor on it
    - it worked fine until I used Migration Assistant to move information from an older Mac to this one

    Any help would be greatly appreciated. I've tried leaving it unplugged, resetting PRAM, resetting NVRAM, resetting all, unplugging hard drive, unplugging peripherals, running it without the back cover with the stand on, EVERYTHING!!!

    Here's what I think: I think that it might be because of the missing hard drive caddy. Is it possible that it would think it's overheating and causing the fans to come on, and then get stuck? Or is it a faulty hard drive? I just bought the hard drive yesterday. Thanks!
  4. 666sheep macrumors 68040


    Dec 7, 2009
    Try clean OS install on this new HDD.
    I don't have any iMac G5 now to test, but i think that absence of HDD thermal sensor could be problem for your iMac. Fans speed is dependent on thermal sensors reads. Lack of one of them could be misleading for iMac's firmware.
  5. raysfan81 macrumors 6502a


    Oct 6, 2009
    North Carolina
    I think this very well could be the problem because all of the fans were controlled based on the temperature and the rpm's would increase/decrease accordingly. Since there is no sensor in the hdd are because the caddy is gone, the fans might be freaking out because there is no temperature reading.
  6. MacHamster68 macrumors 68040


    Sep 17, 2009
    as its a first generation iMac g5 , i would open it up clean it inside and look for bad caps first , as they suffered badly from that issue , and the symptoms vary
    and the iMac g5 had heat problems anyway , so it could also well be the thermal paste dried out which is used to bring the heat away from the processor to the heat sink , so replacing the thermal paste would be a good thing

    imac g5 with following serial numbers are affected from bad caps

    Serial Number ranges:

    * W8435xxxxxx – W8522xxxxxx
    * QP435xxxxxx – QP522xxxxxx
    * CK435xxxxxx – CK522xxxxxx
    * YD435xxxxxx – YD522xxxxxx
  7. ercj95 thread starter macrumors newbie

    Nov 22, 2008
    United States of America
    Capacitors are Visually OK

    The capacitors look fine to me. How can I tell if there is a faulty capacitor(s)? I don't have AppleCare, and don't want to pay for it. Will Apple replace the capacitors? Thanks for the info.
  8. MacHamster68 macrumors 68040


    Sep 17, 2009
    you can see a bad capacitor , most times they are a bit bulged, rounded top , or the top is a bit split , or they are leaking a bit

    and no apple wont repair them apple only is exchanging the board which cost you more the double what the g5 is worth now , apple had a extended repair scheme (apple made that so public back then, that even apple employees did not know about it ), but that covers only up to 3 years after date of sale and only the listed serial numbers , others might have been effected too but are not covered

    if you are lucky dusting and applying new thermal paste will help to solve the problem of overheating but only if you are lucky, otherwise soldering new caps in is your alternative if you sind any that look suspicious

    more info you find on this side its very good for iMac g5 bad caps

    especially this part is interesting what this jim is writing ::
    """Another interesting bit of information regarding noisy iMac G5 fans and internal temperatures that I discovered after the G5 motherboard repair, it became apparent, the computer fans were running a lot quieter. No more Hoover Vacuum cleaner sounds.""""""

    so it is clear that there is a relation between hot imac g5 and the bad caps
  9. ercj95 thread starter macrumors newbie

    Nov 22, 2008
    United States of America

    I would just like to thank everyone for your responses to my question. You dedicated some of your time to my iMac problem, and for that I am grateful. Will look into replacing the capacitors. After visiting Jim's website, some of his faulty capacitors examples are consistent with mine. I'm going to ask a friend (who can solder, I can't!) to have a gander at it. Also will try to obtain a hard drive caddy. I really appreciate the help! :)

    The :apple: community is the best community!

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