Chosen Solution
I have a fat PS3 model not backwards compatible. I gave the PS3 a cleaning in the inside and gave a fresh thermal paste in it artic silver 5. And it still shutdowns when I power it on for a few seconds. The red light starts blinking. I’m thinking that the console thinks that it’s overheating so it shuts down. Is their a sensor that the PS3 has?
As Tommy Gurreri suggests, was the fan correctly connected after the cleanning? Other possibility is did you put too much thermal paste? Notice only a little is necessary. Using too much may be as harmful as using none, because the thermal paste is only needed to fill the microscopic gaps between surfaces, not to create a new layer by its own.
