There are 3 kinds of fan mods for the fridge. One is to simply put in one of these battery operated fans to help circulate the cold air inside the fridge.
Next it to install a fan that blows air over the interior cooling fins. Taps into power from the fridge light switch.
Then there is the fan assembly that blows air into the fridge chase behind the fridge. Info link below pic.
rv fridge fan installation - Bing