Short of turning on the defroster, I'd like to get a solution to this as well.

I don't have an internal fog, though. Instead the cold air inside causes the warm, moist air to condense on the outside of the window.

 

meltdowndave describes the same thing I've noticed on some rainy days. Moist air condensation on outside bottom of window.

 

The windshield fogs up extremely easy on rainy days with IAQS turned on. I just don't get why it's happening. I'm positive the air isn't be recirculated. I once went from outside in the rain to the underground parking garage. 20 seconds later I couldn't see where I was going! Had to blast the AC! Only later did I realize it was the IAQS fogging up the car.

When you guys say condensation, you mean like water droplet condensation?

 

geokilla, yeah its tiny water droplets that form in ovals just outside the bottom of the windows near the vents. That can be dealt with by using the wipers. I've had the same thing you mention from going from rain to underground garage. That was fog and I would also like to know why that happens. I will try turning off the IAQS next time.

 

Correct me if I'm wrong but the reason fogging occurs is a temperature imbalance between the inside cabin and outside air. If the air in the cabin is warmer (and consequently able to hold more moisture) and the vehicle then driven to a cold environment, such as an underground garage, moisture in the air in the cabin will condense on the inside of the now cooler windows. That's just physics and any vehicle will do that. The key is to change the moisture content in the cabin air which would be to bring in fresh air. (or use the A/C or heat the windows)

I'm not sure how the systems is programmed to work but there is a note on page 140 of the owners manual that states

If the insides of the windows start fogging, disengage the air quality sensor. Use the defroster function to increase airflow to the front, side, and rear windows.

My guess would be that if turning off the IAQS is clearing the windows in this situation then perhaps the system is restricting fresh air intake by perhaps employing partial recirculation, for whatever reason, and that only turning off the system is the way to restore full outside air intake.

It would be nice if the owners manual gave more details as how the various systems in the vehicle work for better understanding.

 

Correct me if I'm wrong but the reason fogging occurs is a temperature imbalance between the inside cabin and outside air. If the air in the cabin is warmer (and consequently able to hold more moisture) and the vehicle then driven to a cold environment, such as an underground garage, moisture in the air in the cabin will condense on the inside of the now cooler windows.

Except the inside surfaces of the windows would not be cooled that rapidly by the air inside the underground garage.

It is more likely that the glass was already colder because AC was on for an extended period before entering the garage, or because it was cooled by the rain. Condensation would then occur on the outside surfaces. You can also get the same effect outdoors with AC on and no rain under certain atmospheric conditions when the outside air is close to the dew point.

If AC is off, condensation can also occur on the inside surfaces (even with recirculation off) because the glass has been cooled by the rain and is now colder than the moist inside air. A sudden blast of cold (relatively) outside air from the garage could conceivably make things worse initially by reducing the temperature of the inside air, thereby increasing the relative humidity further and making condensation on the windows more likely.

That's why the AC should always be left on, as stated in the manual, to maintain low relative humidity.

 

Going home tonight, the car was parked outside for a good 9 hours so outside temperature was more or less the same as the cabin temperature. IAQS was on and I noticed that there was fog in the front and rear windows. There wasn't enough to obscure your vision, but enough to know that it's there. It was a dry day too with no rain in a while, so I don't get why IAQS causes this...

 

I'm pretty sure this has to do with the amount of relative humidity in the air. Here in DC we've had a couple humid days recently, during and after all the heavy rains we had. I noticed that I would get condensation that builds up on the outside of the front windscreen, especially when the A/C was in Auto mode. I changed the output to Body and it went away. Cold air interacting with humid air always produces condensation, like a glass of cold water on a steamy day.

Of course a "dry" day doesn't necessarily mean there is no humidity. It's been sunny and dry here but very humid. On days where there is little humidity, I see no condensation.

If anything this could be a flaw with the Auto mode directing too much air to the windscreen vents.

 

If anything this could be a flaw with the Auto mode directing too much air to the windscreen vents.

I doubt it. I didn't feel any air coming from the windscreen vents today. Of course, it didn't rain today so maybe the IAQS sensor didn't sense the increase in humidity or something.

 

It's not the IAQS system which causes fog on the outside, it's the upper vents blowing cold air onto the windshield. There is a very simple solution to the problem when running on full auto on rainy days. While on auto, manually select the body, floor or both vents, the rest of the system remains on auto and the outside fog will dissipate.

 

I think the OP was commenting on fogging of the inside windows. Every car (and home/office window) will fog the outside of the glass if cold air is blowing on the inside of it.

I too have found I had to disable IAQS on those rainy days if not using the A/C or the inside of the windows will start to fog. I only like using the A/C when it's hot.

 

I think the OP was commenting on fogging of the inside windows.

[Mental Note] Read, not skim, before replying.