I've had a 60GB Playstation 3 model since 2007. It got replaced by Sony because of YLOD a few years back. For as long as I can remember the fans goes up to full-speed whatever the console is doing. The noise is the same if it's playing the latest game or is just in the XMB.
So I decided today that I should open up the machine and remove all the dust. So I opened it up and when I got to the big fan, there were almost no dust at all. I closed it and started it up again and the noise is still there.
Could it be so simple that a heat sensor is broken? The HDD has been replaced a number of times so maybe if there is a heat sensor at the HDD that I can replace? Can that be the problem that causes the fan to go to full-speed and make all that noise?