I 'think' that the OP may have been referring to a solar powered fan for improving the refrigerator's exterior air flow - not the little fans that only circulate air inside the refrigerator.
If this is the case I'd recommend first getting the refrigerator, or how the RV manufacturer installed it, checked out. I'm not aware that all RV refrigerator installs usually require exterior fans to increase exterior air flow if they're built-in correctly such that natural convection moves air from the lower RV wall intake opening up past the back of the refrigerator and out a large enough opening in the roof.
So far, ours has always operated fine in any kind of (high humidity or low humdidity) heat - if: We don't load it up inside too much, we keep the RV level as we should, and if we have it's 5-level thermostat control set to 4 instead of 3 in extremely not weather.