Thank you for the great responses. The suggestion to go to the thermostat gave me a "Duh" moment for sure.:S Will have another look at things tonight. If I can control the furnace a simple switch install for the fan and we are good to go.
Wes the ventilation fan is not ducted however I have not seen any evidence of condensation as of yet nor have I heard of this being an issue. It's bone dry under there whenever I look. We have 10,000 k on it and over fifty nights so far. Have not had it out for winter camping yet but will definitely keep an eye out thanks for the heads up.