Dodge Caravan 1999 windshield fogging

I drive two 1999 Caravans, a base model and a Sport. With both I have a persistent problem with moisture in the heating/cooling system. When I turn it on, it smells and feels moist (not like coolant), heat or A/C, summer or winter. I have pressure tested, no leaks. I have replaced heater cores, o ring seals, checked the condensate drains for blockages, replaced the metal tubes that go through the firewall on one car. There is no moisture coming from the outside-- we are in a drought here in California. The windshield starts fogging at about 34 degrees and gets so bad when it is colder that the defroster full on with the A/C on cannot completely clear the inside glass. Really cold (for us) 20s and the windshield is so fogged that driving is scary. When I drive into a cold spot in winter, sometimes the whole windshield will fog in a few moments-- that’s with the defroster on. Anyone have any suggestions? I and the mechanics I have consulted are stumped.

Is the fresh air door opening? When using defrost it supposed to be drawing in and dehumidying fresh air.

You are turning the temp up, right ? And you don’t have it in recirculate mode?

It sounds like you’ve done pretty much all that can be done. I’m surprised you haven’t found the problem yet. hmmm … well, one simple thing, you could lift the carpets and make sure there’s no water under there. And you could check the coolant level week by week to see if it is going down, which it shouldn’t, or at least no more coolant loss than a half cup in 5-10 thousand miles.

Besides that, the only thing I can think of is that one or more of the vent door actuators has failed. It may be you are thinking your are drawing in fresh air, but in reality you aren’t. Checking those actuators can be a fairly difficult job is the problem. I’m wondering if you could work up some way to create a supply of visible smoke, like a cigarette maybe, and hold it near the outside vents under the windshield, and see if the smoke gets sucked into the vents when you have the system set to fresh air vent mode.

My Dodge mode motor went out after only 3 years. I could hear it clicking and only got defrost and no air through the vents.

I haven’t checked the door actuators-- will do that; they seem to be working. I have been pushing the recirc button with the defroster on high heat and fan, because that seems to be the only combo that clears things when it is really cold. I will try it without the recirc button pushed next time. There is no loss of coolant or moisture on the floor. Thanks!