I've got it on one, right on the edge of the off switch ... I did have it up higher, and it got below freezing when it was empty. I actually went out and bought a fridge thermometer to confirm, since I didn't trust my mash therm or my wife's cheese therm (suited as they are for higher temps). Still the same numbers--maybe I ended up with a random superfridge, though that seems odd. So how does the fan fit into it? I don't have one--is it something freestanding, or do you wire it in?
goto radioshack or bastbuy and buy a muffin case fan. make sure its 12volt. then get an old cellphone charger and cut the ends off. use a vom and find which is poss and neg. then wire that into the charger. if you wanted to keep it internal check the switch for constant hot and wire it into there just make sure you use a 110 fan. you just need the air to circulate so you can mount it to the top or you can use some pvc tubing and mount the fan into it and blow the air up or down. i was at homedepot looking at pvc the other night and think i will try to come up with something and take pics. i have a bunch of muffin fans laying around