I agree your's had a defect and regardless if it was a defect right from the factory or a defect over the time of ownership, unfortunately it didn't show itself until after the glass defect warranty period expired. Not much you can do, sucks but dwelling on it won't change anything. Get it fixed and move on, it didn't crack because of the heater alone, like you said it had a defect.
Where in the world did I say any of that. I also live in Alberta, however in the city, where they are heavy with sanding, and sometime the sand is a little bigger than sand. When you are on the freeway going 100kmh and you get hit with that, you get chips. You put your defroster on with a chip and you get a crack. Not using your defroster in Alberta is not an option. Paying $1200/year to change glass is also not an option unless you are rich. What I said, its the norm here to just leave the chips and cracks because its just going to happen again.
Keep in mind one thing. The windshield is an integral part of crash protection for the vehicle, both from incoming objects and structural integrity, such as a rollover event. Yours is compromised.
!) If you have comprehensive insurance that should cover it.
I can only think of one thing that would explain this. In a conventional ice vehicle, the engine heats water which heats the cabin. So when you start the defrost on an ice vehicle. It heats up much slower rate and gently heats the windshield until the water in the coolant system is 195° or so. In an electric vehicle the windshield is very cold and the heat is much quicker. I think this could be the reason why your windshield is cracked. Just a thought, not a scientific fact. When I was a kid, I had a kid that would make glasses out of bottle bottles. You would lay the bottle on a rotating device and score it, and then heat it with a candle and put it under cold water to make it crack. Then sand, the edges, and wallah you had drinkingglasses.
I do not doubt cold glass and hot temps do not mix. However, theses are laminated windshields with special properties. Ford sold approximately 75,000 Lightnings over the last three years. I am pretty sure they did an engineering analysis when they designed the windshield defrost system. This gentleman's windshield had an unidentified flaw it it that most likely caused the crack. Search this forum alone, you only get two threads on windshields breaking for unknown reasons. If this was a design flaw, you would have way more cause a lot of these trucks are in super cold climate areas.
Ford calls it “sound screen” it’s printed o. The glass near the bottom. Same glass for ice f150’s, PB and lightning.
