Hey jsimmy - welcome to the forum! Glad you found us. If you get a chance, come on over to the new member forum and introduce yourself.
The fridge is pretty simple, so other than looking for the obvious (obstructions, damage, etc), I dont know of anything else to tell you to look for. I would recommend you go to the manufacture site and see if you can get the operations manual.
Remember that it takes quite a while to cool down so dont expect to feel any cooling for up to several hours. On the 3 way - it will take a lot of power to run on 12 volts and usually will not cool that well. They seem more suited to keeping cool after the initial cool down.
Enjoy and let us know how it works.