or it's your INVERTER external fan, installed by Thor, to minimize hot temps in the bay where the Inverter is located - it is powered thru a temp sensor, running the fan until the bay temp falls below it's set temp. Sometimes the fan seems to run non-stop, even when you know the bay is already cool.
to 'test' this sensor: apply a piece of ice to it temporarily and see if it shuts off the fan. The sensor is generally wired in the same area at the inverter, but sometimes part of a bundle of wires - usually a 'round' looking small device.
'14 Palazzo 33.3 bunkhouse 34' diesel
KingTailgater2 Dish HD, 100w/5a SOLAR, BlueOx
110,000+mi since '14 - US, Alaska, Canada (also, '14 Gulfstream Amerilite and '07 ForestRiver Rockwood) : )b