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I have a mid 2007 imac 24" intel duo core My problem is all of a sudden it started the fans running high, runs for about 15 minutes and then the screen shuts off. The fourth led goes out and that is it, everything stays on and the fans are still on high. Also I took it apart and blew out the fans and dust ( it wasn’t that bad, but I could not get at the fan behind the main board yet ) When it is running nothing feels hot on the back or front , but I did notice that the upper left back corner was extremely hot and now it is not. Could a faulty sensor be the problem? Here is a read out of my settings Temps HD. 38 degrees Celsius CPU. 30 Airport card. 55 Ambient. 22 GPU. 110 GPU diode. 126 GPU heatsink. 126 HD bay. 41 Fans Optical drive 699 rpm Hard drive 1291 rpm CPU fan 3309 rpm Also it does not need to be unplugged to restart.

After it has cooled down: Start up from your system installation disk or secondary disk while holding down the “D” key until the AHT (Apple Hardware Test) starts up. Run it and let us know of any codes it gives you.

Darren - Did you jumper the HD SATA I/O speed down? Newer drives are often SATA II or SATA III while your system’s interface is SATA I or SATA II (depending on your firmware) which is likely the root problem here. You see, your system is constantly trying to read/write to the drive but is having a very hard time accessing the HD which is why your CPU is over heating. You could try accessing Activity Monitor to see what processes are running and what is using the most CPU. I would also run a temperature monitoring app like Temperature Gage from the App Store to see what is over heating. This app does logging so it can catch the temp just be for the system shuts down on you.

Darren, the only way to permanently fix the symptom is replacing the video card. I can confirm this because I just replaced my video card. I do not have GPU overheating issue any more. I have been watching full HD online movies for several days (stress test for the card), the overheating issue is gone. The highest GPU die temperature is 61C, normally it is around 50C without online videos. Before replacing the card, my old card can easily reach 128C in completely idle. I have been trying many ways to fix the old one, however none of them worked. Ways I have tried:

  • replacing GPU heat sink compound
  • adding an extra heat sink to GPU
  • removing air wall under GPU
  • reflowing GPU (the GPU died after this, don’t try)

I am having the exact same issue that Darren has, and I just bought a new GPU, and it didn’t solve the problem. It’s almost indisputably a logic board problem, but the logic board looks beautiful under a microscope. Can’t find anything wrong with it physically. I’ll keep looking. If anything comes up, I will post it here.

I can confirm Tommyjames337. I have exactly the same problem. Had the GPU replaced and the problem is still there. The hard drive was replaced some time ago, and the problem didn’t start then. So there must be another issue. Unfortunately the imac doesn’t run long enough to finish AHT.

I have iMac9,1 which is from 2007 that works for about 20-30 minutes. After that the top quarter of the back gets hot and I can hear fans slowly getting louder. After about 30 minutes the fans get very loud, the screen freezes and everything on the imac freezes as well. What hardware do I need to replace? It’s such a nice computer and I dont’ want to toss if I can upgrade some parts. Thank you Livia