The first gen model of the Playstation 3 got very hot, so hot that the solder that held various components connected to the motherboard would often melt. When this occurred the hardware components would break the connection with the motherboard and cause a flashing green light which would eventually turn into a yellow light. This is known a the Yellow Light of Death or the YLOD. This video guide will show you how to repair the YLOD on the fat PS3.
There are lots of guides that explain how to solve this. Some involve using a hair dryer or some other form of heat. A lot of these can temporarily fix the issue, but it never lasts more than a few weeks. In order to fix this issue in the long term, you will need to find a way to repair the damaged solder. This guide will explain how to do this and repair a broken PS3.
This repair process involves using heat and you need to be careful that you do this correctly. You risk permanent damage to your PS3 and anything else you use to during this repair If you do not follow the instructions perfectly.
This fix is a long-term fix, but it is still likely that the YLOD will return in the future. The issue is caused by the PS3 generating too much heat and this is something that cannot be fixed unless you upgrade to a newer model. Once you have repaired the YLOD you need to make sure the PS3 is in a place that is well ventilated and has access to cold air with the ability to easily get rid of any hot air that comes out of the side vent.