From your description I am thinking that the A/C drain outlet is blocked. On newer cars they run the air conditioning while in defrost mode to help prevent this exact situation. It dries the air out so you do not get ice. If the drain was blocked the moisture just backs up instead of draining out. Then when you turn the defrost on it draws the air across the water and just like air across a lake gives you snow, you get ice on the colder windows.
The drains usually look like a ruck bill at the end of a short hose. The bill keeps the hose shut against bugs and dirt while allowing water to drain. It will be located low on the outside of the heater/AC housing under the hood. Squeeze it to open the bill and use something to poke inside to clean it out.
Tuesday, December 13th, 2016 AT 7:09 AM