My Ac should work fine. Worked great all summer. I don't think its that, but I guess it could be. No way for me to tell if thats it since it 35degrees outside.

I don't feel any water on the passenger side floorboard. Occasionaly I will get a musty smell, so maybe its leaking elsewhere.

I do not have the re-circ button on so that shouldn't be it unless the damper is not opening. How can I tell if the damper is opening?

I'm wondering if its the heater core, and will need to look closer.