For the last two days my Wii has powered down while I have been gaming. I noticed the console itself was getting really hot. After checking the console a bit more I noticed the back fan was not working at all. This caused the box the over heat and shut down. I checked out these forums and a fwe more for a fix on this. Basically there is one solid option that I read. Get the fan fixed (duh).
I didn't want to wait 10 days for my wii to get fixed so ignoring the advice from the boards I went and got an external fan for the Wii. From what I have noticed all the threads about the external fans are correct. They are not a good fix for over heating Wii's. BUT!!! When you combine both the back external fan and the base fan it cools the Wii like nothing else. I have had my Wii running non stop playing Mario Galaxy for about 14 hours now. Not only has the box not shut down but it is cool to the touch. It was never cool to the touch even when the back fan was working.
The short is. If you need to cool your Wii buy both the external back fan AND the base fan. It works. It works great.