The short of it that there is a senser that turns from low to high. It is activated by a thermocouple. I was miss understood earlier, I was trying to say that if stick on high speed it is not always a heat issue. It may have got super hot and then the fan is stuck spinning high.
If there were an easy fix, easy answer you would have 5 post of people trying to help with solutions. I am a electronic tech and these things are mass produced and with sub par engineering. Dont get me wrong I love my ps3s but you would think for the price we pay at stores they would work.
I have a sony home theater system, I play that thing on max vol. everyday for 8 years and never one problem. COUGH COUGH ...CONSPIRACY to buy another because sony loses money on every system, they count on software believe it or not. And this JB is really opening there eyes to much larger profit losses. ANY WAYS good luck bro