When your Playstation overheats to the point where it damages components within the unit you will see the yellow or red light
. Both of these lights can also be because of the Power Supply Unit failing. Whatever the reason, both of these problem prevent you from playing your Playstation. Most people spend lots of money on games and accecories which no longer are useable because of the broken PS3.
Both of these issues can easily be repaired by the owner. If you would rather send your unit to Sony and pay a hefty repair fee, then go ahead and ship your unit to them with a check for $150+. Don't be alarmed when you receive a refurbished unit on your door step after 5-6 weeks. These refurbished units only have one part replaced in them, there are still plenty of worn out parts that could go bad at any time. You have no clue how the previous owner treated there playstation 3. I don't consider this a very good investment.
There is currently a guide called PS3 Fixer, which shows you step by step how to fix your Playstation 3. This guide doesn't cost you upwards of $200 that Sony will charge you, and you can have your playstation up and running within an hour, instead of waiting 5-6 weeks for your repaired unit to arrive. You also know that the unit you have has been taken care of, it hasn't been dropped or had stuff spilled on it. You can reada review for PS3 Fixer here.