There is a company that makes a fan/light assembly that goes INSIDE. I tapped into the fridge light circuit to power it... Worked very well and greatly reduced icing of the fins.
Fans outside also seemed to help (Tapped into the other end of the same wire) but when the cooling unit failed the technician showed me where crud was blown up against the heat exchanger... NOW IF I were still RVing... I'd now know how to clean that crud out (Blow air DOWN, carefully, fan off cover off) but alas I'm no longer RVing.