difficulties to switch on my iMac when it was cold
As my problem is quiet the same, I don't know if I have to open a new topic?
For sometime, I had more and more difficulties to switch on my iMac when it was cold (after a night or more, I had to reboot it up to 30 time to really wake it up!), and a lot of sudden "sleep mode" with anything to do but reboot it…
Few days ago, finally refuse to boot:
no gray screen, no sound, just the light on in the right corner… and a new weird sound when it tries to boot!
After trying everything I could (reset PMU, PRAM, change the ram etc etc), I decided to open it.
I cleaned it of all the dust accumulated in 2 years (when I changed the original HD) and checked everything I could, but I didn't notice anything suspect.
The 1st LED is lit when the cable is connected,and when I push the power button, the 2 and 3 are lighting up too (and stay lit), and that's all.
The fans are on, everything else seems to light on, but there is still the same unusual noise and the display stay black and the HD don't seem to start up.
Only the white light (on the right beneath the display) stay lit.
I strongly suspect the power supply, but before buying a new one, I'd like to know what you think of it : )
If some has a clue or an advice, it would be great!
And sorry for my english… I'm a French ;-)
Update for this issue:
it was in fact the Graphic card, a known issue on a LOT of iMacs!
To make it "work" again, you can disable the extensions (press the shift key at the boot):
it should work but with no CG acceleration and a lot of other thing H.S…
If you can find the specific extension for the CG, just remove it from the folder (on your desktop for example) and reboot normally.
You should be able to use you iMac nearly "as usual", but without the graphic acceleration…
If you want to try to save your iMac, you can try to remove the CG and to "burn it" ± 10 minutes in an oven!
You can fin some tips on the web, the process is different for each iMac model, but it worked several time for me:
With a 27 iMac i7 2009, perfect for 4 years and maybe more:
the iMac was stollen…
I also did it with 3 24', it worked with one for a year or 2 before doing it again.
Another worked for a few days only, and the 3rd stayed dead.
Anyway, if you are ready to throw away your iMac, it's worth trying (but follow the process : )