The fridge won't interfere with the a/c, but the a/c will interfere with the fridge.
One thing to remember is the a/c unit will both pull air into the sides and exhaust out the back. These need to be separated from the two. Same with the front. With the a/c unit enclosed in the camper, the exhaust will get pulled into the intake and keep it from working quickly. There won't be enough ventilation to keep the air cool.
What you could do is set the a/c on the roof and then make an enclosure to handle the inside air, part for coming into the a/c and part for the exhaust. Exterior air won't be a problem since the unit is outside.
Don't forget, you also have to worry about the water dripping from the unit. Sitting on the roof, this can just drip on the roof and run off the side of the camper. If you put the a/c above the fridge, how are you going to ensure the water is properly drained?
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