Try setting the thermostat to "Fan", then use the "+" and "-" keys to set the fan to "Auto". Then switch back to "Furnace" and see what happens. It is possible some sort of electrical noise or voltage spike when connecting to shore power caused your thermostat to reset to defaults - which may have set the fan to "Hi" or "Lo" which would result in the fan running with the furnace. Many of us have experienced the AC fan running with the furnace and have solved by doing the above.
2012 Solera "S"
Calif SF Bay Area