Did it sound like the fan on the inside of the RV? Take the cover off from the inside (only 6 screws hold mine on) and you can see the squirrel cage fan. Otherwise only 4 screws hold on the outside cover (But you might see a live squirrel so be careful!).
Or could be Santa elf caught in the fan since you didnt have a fireplace? Ho Ho Ho. LOL.
2017 Axis / 25.4: Big Foot Levelers, Aims 1200 Watt inverter, Ceramic Window Tint, Full River AGM 6V batteries, Front Hellwig Sway bar / Rear Track Arm, Safe T Plus Steering Stabilizer, PD 4655 converter, Hard Wired Surge Guard, WEboost + WiFi Ranger, LED Headlights/Driving lights, TPMS, Surge tank, Tornado flush, Viair Compressor