Call Thor customer service, 877-855-2867 ext #2 then #1, have your VIN's last 8 digits. Tell the rep your issue and ask that it be recorded for warranty. Ask for the heating drawings, these should show how the ducts were run. While your at it, ask for the all electrical and plumbing drawings too. And the framing, roof, floor, slide-out, etc. Be nice, it goes a long way.
I'm wearing trifocals now but my hindsight is 20/20.
Bilsteins and Sumos front and rear...HUGE! FatMat and Hoodliner...HUGE!
Hellwig sway bars F&R, 235/85 Hankook ATM, alignment...HUGE!!!
Battery watering, 260watts Solar and BigFeets to make life easier.