You talking about your refrigerator or the a/c : air conditioner? I have yet to hear of running the a/c on propane. I understand that if you put a sun blocking shield over the side of the RV where the fridge vents that will help. Reflextrix should work well and you can get that at Lowes or Home Depot. Some people install a fan inside the fridge and/or behind it.
For the a/c pull the cover off and clean the coils. Clean the filter inside.
Generally most people think that the fridge cools down faster on electricity.