MookieKat wrote:
How do you add the fans and where are they installed?

This isn't my setup, but you get the idea. I borrowed the picture from the ebay seller where I got mine. The fan has an alligator clip that acts as the ground. On the 12cf model, you can't wire it to the light. I had to run the wire down the drain tube and tied it into 12v power at the controller.
I have 2 of these in a 12cf. Normally 1 does the job, but if we have it packed extra full and the ambient temp is above 90, the second fan helps out. Using one of these, you don't get frost buildup on the cooling fins either. I haven't found anything negative about these yet other than increased battery drain if you are boondocking. Even then, I think each fan only draws less than 0.14 amps.