Heater and condensation

Sounds like like you have cracker heater core. Does it smell like anti-freeze?

It was the first thing that I thought of. But no - there are no suspicious smells. Although people told me to run few days with opened rear flaps and leave them open during night. Will try this solution for now...

On the other hand, sometimes I smell dry dust in a car. The smell usually came when heater switched to a "window" position. I know how tosol (coolant) smells, but this is not the one... or I'm mistaken? Are there any ways to check have i cracks or not in my own garage, not giving the car to "professionals"?

I have the same problem.Winter or summer. My caravan produces moisture and even steam. Water is only produced by the A/C. If it doesn't drain it stays somewhere in the car (in winter this water freezes and takes about 1/2 an hour to melt - no problem on short trips in the city), the air ventilation passes over the water and picks up moisture from it and deposits it on the windshield and or windows. In cold temperatures it freezes. I had to drive in minus 27ºC - My wife and I had do scrape the windshield free all the way! Then suddenly hot steam fills the air, 5 minutes after the steam stops but half an hour later it comes again. What produces steam. The water that doesn't drain (A/C produces and adds more water) finally touches the heater core and creates steam or hot very humid air. In summer I can drive for fifty or hundred km, than suddenly a blast of steam and you can't breathe and straggle to open the windows. It's hotter inside than outside.5 minutes after the A/C works again normal. Mechanics and dealer tell me it's not possible but have no better explanation nor do the want to fix it.