If you are running an exhaust fan, kitchen or bath, air will back-draw from any trap or seal that is not tight. Be sure your toilet is sealing, will it hold water on the slide when not in use?
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[SIGPIC][/SIGPIC]2008 Bounder 38P F53 24/30K V10, 2013 Kia Soul Basic 6 speed manual, Ready Brake Elite tow system (previous equipment 1996 Pace Arrow Vision w/Acme Dolly)
Guessing but perhaps air intake for A/C and the ambient breezes. When wind is right and A/C on, wind over the roof vents blows the vent gas toward the air intakes.
We had a similar problem when going down the road in our class C. When I rolled down the drivers window it created enough of a differential as to suck the vent gas back into the coach. Smell would go away after stopping so had a heck of a time finding the cause.
Same with us , we have to keep the drivers window up.
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2008 KSDP/2013 Flex
2nd year Fulltimers and still loving it.
We had this problem in our 2006 Suncruiser. Turns out that the ac duct system from the basement ac unit up behind the rear cap had a leak. As it was pumping air out it in turn was causing negative pressure in the coach. This would pull air in the coach from any where it could. In my case it was many places including the smelly holding tank area. Put a plastic bag over the window with the it down ac running and see which way it goes. If in than that could be it.
Jesse
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You Only Live Once Travel!
2013 Winnebago Tour 42QD
Apopka FL.