Hi - my 2000 Ford Windstar has always had foggy windows in cold or damp weather. The back side windows cannot be defogged, and it’s almost impossible to keep the front side windows clear - the windshield can by clear as long as I keep the defog on high all the time. It has gotten worse over the years - we have replaced the cabin air filter, but it did not help. Thanks!!
It’s your heater core. Same thing happened to last week.
It is a possibility it is the heater core. A loss of antifreeze and the smell of anti freeze are two definite signs. The fogging of the windows is because there is a high moisture content inside the vehicle. If you can locate the source of the moisture you can fix your problem. I have found kicking the snow off your boots can help prevent the problem, but when I take 3 kids to school it takes a bit to dry out the air, the best method I have found is to have a window partially open and defrost on high,
You may have a chemical film build up on the windows. If so, it makes them fog much more (in cold weather) than they would otherwise. Get a spray can of invisible glass at Wal-Mart and follow the directions on the can. Buy some lint free clothes while you are there to use with it. It makes a big difference. Also, always run the AC compressor with the heater or the defroster to remove excess humidity.