Live and camp in hot, muggy Florida. Installed these (2) one on each side at the bottom. Fabricated a mounting bracket from 3/4" alum. strips for support. They're really quiet and seem to do the job improving air flow. They're 110 v not 12 volt. Used a three way adapter where the frig plugs in. Eventually will run through a relay so I can run them as needed from inside the coach without going out and pulling the vent cover and turning them on. Not really an issue though, just added convenience.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1