Hi sadly a ps3 i bought has developed the ylod.I striped the console down right to the motherboard and heated the GPU and the CPU up to 350c with an heatgun. It worked for me for about 10hours, Now it's gone again and has gone back to the ylod .i am thinking of doing the heat gun trick again but wiring the fan up to a 12v feed in the power supply (thats if there is one) also adding a fuse to the wire so that it carn't set on fire if i have any power surges.I think if i wire the fan up it will spin ultra fast and cool the motherboard a lot more inorder for the solder not to melt.Also i have a question about the motherboard, Do the motherboards have a technology also known as smart fan?I know it's when the Cpu or Gpu get hot and the sensors detect that it getting hot and produce more power to the fan.
I think the PS3 uses a 3-wire fan, with speed controled by voltage, based on the temperature of the Cell (possibly also based on the temperature of the GPU). However, I have never tested this theory, and it is possible that they control the fan through PWM on the ground. Either way, you can set the speed to max by diverting the power and ground wires from the mainboard to the power supply.
There are several different versions of the PS3 power supply...but I know that all the "Phat" units have a 12v and a ground, and I think all the "slim" units do as well.
If you were to run a 12V and ground from the power supply to the fan, you would not need a fuse to prevent fires...the power supply is already fused to prevent fires...and most of the consoles use high quality fans from companies like Delta...plus, I have NEVER had a fan start on fire in all my years of building computers...if they start getting hot, they will either short out, open circuit, or sieze up...fire would be almost impossible without an existing flame.