Same story --- my 2.16GHz 2006 white iMac started to show all kinds of ill behavior (graphics noise and strips, completely garbled graphics, and system-hangs) all related to heating.
Following the tip I found here -- I installed smcFanControl, and it improved things for a while. However, it deteriorates over time, and now I can't use the machine unless the air conditioning is turned on in the room.
It starts to show signs of malfunction as soon as smcFanControl reports anything over 31celsius (round 90F).
Our area is very dusty, and I'm quite sure some cleaning can improve things again. However, I'm quite sure it can't SOLVE things.
In addition --- the internal superDrive stopped being able to eject discs, which again is something reported here. Up until now, I couldn't find reasonably priced internal replacement drive -- but now I saw some ~$90 used drives here.
I guess it is time to open the machine... My questions are:
1. Are there any detailed tutorials for replacing the GPU card?
2. Did anyone actually replaced his GPU, and (the iMac) lives to tell the story?
3. Where and How can one purchase the right GPU card for this rather old machine?
4. Are there any specific recommendations here for replacing the internal HardDrive (upgrade for bigger storage) to something which also RUNS COOLER ?
I never took apart this iMac, and the tutorials for replacing the optical drive don't exactly encourage me to try. Prying open the case seems a little dangerous - I could break some of the levers, or something).
I dealt with lot's of electronics in the past, but I remember macs to be a delight to dismantle (orignal Macs, Mac II series, Quadras, PowerMacs, PowerBooks G3 G4 and G5 Towers, Intel Mac Pro's and many others --- however, this seems to be very different, and very risky ---
I need some encouraging here :)