long road trip during the summer with my AC blasting when I noticed fog-like air coming out of the vents. I shut down the AC when I saw that and opened the windows in case some sort of toxic gas was introduced. When I went to turn it back on, no cold air ever came back out of the vents. It was that moment when my AC system failed.
I wonder if the fog is more than just a high amount of humidity. Or maybe it's a case where the ducts are still cold from previous cold air (up to the point of AC failing) and now warmer more humid air is being introduced, giving us a fog-like visual out of the vents.