Windscreen fault

[Nova Invicta]

First time I used the windscreen demister / de-icer the windscreen cracked behind the rear view mirror this has now spread to one third of the screen and Audi UK dont have replacement windscreens in the UK for two weeks! Not what you want to happen nine days after taking delivery of the car.

[Andy]

Nightmare  Is it still driveable?

[sduford]

I had the same thing happen the first time I turned on the de-icer on my 2005 Outback XT. Turned out it was an improperly installed windshield that caused extra stress on the glass. The temperature change was too much for it.

[kleinbus]

Sudden terperature change is something that should be avoided.

So for example, in the middle of winter you have vents down and middle, no windshield and engine is hot giving you hot air, you go and change down and middle vents off and all to windshield to defog -> you will crack as sudden thermal expansion is too much and expansion is not applied to whole window area.

I have seen this happen to cars, vans, busses and 18-wheelers.

Also it may not be your fault as like one earlier post stated, internal tension cracks windows once a while. Hands on example, I got rock hit to windshield, went to car window specialist whom I knew is professional. 1st glass cracked during installation, 2nd too and 3rd was the one that didn't have manufacturing defect. Lucky me window company haves policy that if window breaks during installation then their insurance pays it and as they had glasses in stock they just took next one.