I may be off the mark with this, so excuse me if you've already tried or known about this.

I had (have) the same issue with my xfire. Here in Scotland we get very few days when it is necessary to use the AirCon, but I noticed that if I used it for a while to cool down the car, then switched it off again, the fog would appear and you are right - it happens so fast and is really Dangerous.

Asked a couple of mechanics I know and they explained the way Air con works... As well as cooling the air, it also takes the moisture out of the air (hence the reason it clears the windows so fast). It is also effective at doing this even if you have the heater controls at hot and turn on air con - the air will blow hot but is still "conditioned" and therefore much dryer.

The fog problem (for me anyway) they reckoned was caused by the fact the moisture taken out of the air when the aircon is on was sitting in the system and when I turned the ac off again, the air would get humid right away and cause the fog. (I should add that even when it's hot here, it is very humid and this doesn't help). Having the drains checked (all clear) didn't help. Only solution I have found is to run the heater at 5 and anywhere from white to red temp for about 10 mins to let the moisture clear itself. Only way of not killing yourself is to keep the windows open while doing so.

If you need to clear in a hurry, Air con is the way - no matter how humid the environment. If it's not working, you have a problem somewhere.

Hope this is helpful.

 

Hi,

We had this problem, the fix is simply take it to the dealer and have a new compressor fitted, the a/c is meant to cut in to dry the air... it doesn't, and that's where your fogging happens.

 

I will bet it is the recirculating switch. I make this mistake a lot in the fall and spring when it is cold in the morning but hot when we go to lunch. When heating make sure the recirculating switch is off. This will cause you to fog up!