Regardless of what setting I have my heat set to, all my windows fog up if the temp is below freezing outside. I live in Colorado, and it happens here - but it happens much, much worse in places like Iowa where the air is more humid. I have my defrost turned on obviously, and it still happens. I had to take it to the dealership NINE times!! Each time they say they can't reproduce it - during the day, the sun is bright enough or it's warm enough outside to make it appear fine. I've had it at two dealerships for this very issue, and the second finally replaced the heater core for me at no charge. That didn't do a damn thing. The problem mostly occurs at night, the colder it is, the more fog I get. I have to have the blower on the dash and in the rear set to 4 just so I'm able to see through holes cleared in the windshield. The more people in the vehicle, the worse the problem is obviously. It's like the humidity is not being cleared out, which is why they always check my AC compressor. They tell me it's fine - but when the fog gets bad, I can hear the compressor kick on for like 10 seconds, then kick back off, then back on, back off, etc, etc.

My thinking is that the little flap that controls whether I'm getting outside air or inside air is defective. Anybody else seen this?

 

If the A/C is cycling OFF and ON every 10 seconds, then it could be low on charge or a faulty pressure switch. The A/C should always run when set to DEFROST. Your damper door could also be stuck to the RECYCLE setting. This will also cause the windows to fog in the winter time regardless of the setting. I would check to ensure that the damper door moves correctly between OUTSIDE AIR and RECYLE AIR to eliminate that. Place in DEFROST and the fan on the HIGH setting and see if you can hear or feel air being sucked in under the dash on the passenger side. If so, then the damper is stuck or broke. Good luck.

 

Thanks for the reply - I had the dealership check my AC system, and they then charged me $150 to "top off" my AC system and check it out. They claim it works fine. I disagree. About that damper door - I'm very curious as to how I can check that since no matter what setting I run heat or AC on, I get a nasty mildewy smell. I had the dealership clean out the system and the smell went away for a single day - then it was back after a trip where the windows were foggy the whole time. I think you might be onto something concerning the pressure switch for the AC system, I'll have that checked out.

 

confirm that the A/C condser drain is not clogged. Run the A/C warm moist environment and check for water dripping just to the left of center at the firewall as well as the drivers side rear behind the tire for rear A/C equiped. Additionally, replace the cabin filter and check to make sure the cover is installed correctly. Last, do you live in an area were the trees have small leaves or seeds, these can and will get under the cowl between the hood and windshield bocking the drainage ports and causing water to get into the blower and possible it to the car. (had an 93 Escort that the heater air intake was allowing water down through blower due to leaves clogging the area and the drains.

 

heater core issue.

 

The van is now fixed - and it wasn't the heater core, even though the dealership replaced it thinking it was the problem. So, as I stated I had the van into two Ford dealerships a combination of 9 times from the day I owned it for this very issue. I bought the van BRAND NEW off the lot. Neither dealership could fix it.

So what was the problem you ask? The motor that opens and closes the air vents to switch between inside air and outside air - it was unplugged. It came that way off the damn assembly line. I had my neighbor (a GM mechanic by the way) come over and look at it with me. In under 2 minutes flat, he determined air wasn't being sucked in from the outside (by lighting a cigarette and holding it front of the winshield), and reached under the right side of the dash and said "Now if this was my van, I want this plugged in..." Seconds later for the very first time, my van was pulling in air from the outside.

No more foggy windows which is great - but why over a 3 year period and 9 visits did neither dealership check for something this damned simple?