answer:You may have squirrels or other rodents making nests under the hood. Ever have an acorn fragment fly out of any of the ducting when you turn on the blower after the summer ends? That’s a dead giveaway. If there’s little or no air flow out of the vent, then your duct is blocked. Because if you don’t have excess moisture in the vehicle, and you do have air flow, then your glass will clear. So I’m about 90% confident that you have a blockage in the duct. For me, mothballs tied up in nylon stockings under the hood of the car has helped to keep the ducts clear, and I can put up with the faint odor of mothballs in the cabin.