IMac – Normal operating temperatures and fan speeds for mid-2006 iMac

It's the fans. They are clogged with dust and other debris from the years of use. Notebooks are not air-tight and intake quite a bit of air over their lifetime (they need to push the air to the central components like the CPU/GPU to cool them). The units must be opened and cleaned periodically (depending on environment) to maintain peak operating performance. High fan speeds and poor thermal dissipation are signs that the fans aren't doing their job (they are likely clogged with dust and the exhaust is also likely blocked, preventing the output of the hot air blown off from the processing units). Computer fans work by pushing air taking from the environment onto the CPU/GPU. The hot air blown off the chips move through air vents in the back of the unit. Over time, dust settles on the fans, dropping their efficacy, and the vents, preventing the hot air from escaping. This bakes the components and results in the spike in over temperature.

Visit www.ifixit.com and pull up a guide on how to partially dismantle your notebook. If you are not technically proficient, bring it to a credible repair shop.

There are no "normal" operating temperatures for Apple notebooks, but there is an acceptable gradient. 82 degree Celsius is pushing the limits. The CPU's thermal threshold is 105 degrees Celsius (when that temperature is reached, the system will shutdown to prevent thermal damage).

And just an aside, regardless of locale, all temperatures should be reported as Celsius, never Fahrenheit when dealing with computer components. Official documentation always refers to Celsius.

Recycle or sell it for parts. Since the GPU is soldered, you likely cannot bypass the temperature sensors that the system monitors to ensure safe operation with consumer skills at soldering. Have you looked into a logic board repair or buying a Mac with a shattered screen at low cost to assemble one workable Mac?

Operating a machine where you know the protection mechanisms are shutting it down to prevent overheating and persist in doing so, being frugal crosses a line into taking risks with fire if you don't go to great lengths to protect yourself and other property nearby.

Also - your characterization of design flaws seems unsupported with one link to a 540 entry discussion thread. A six year old computer having failures seems more like a car needing an engine rebuild after things start failing and not so much a design failure, but perhaps the link wasn't correct.