I have read in my MH book that you should put a fan in the refrigerator to help circulate the cooling. I have placed a battery fan in there before, but as it gets cold the fan stops as the battery go...
I have a fan that I bought on Ebay for less than $15. It clips on th fins which also provide the neg battery source. The hot wire goes to the permanent 12v ahead of the frig light switch. Mine has been humming along for about 3 years.