Mine did it too, tiny chip on the edge, watched it slowly run before my eyes, no defroster on even. It got hit , stopped jeep, got out, could only find a tiny and I do meen tiny chip. I said awe that don't matter, started driving and watched it grow. Damn glass shoulda had a rubber seal around it to at least protect the edges.

 

I think you have some damage to the windshield that you didn't see.

 

My windshield cracked too. Crack started up from the middle, went a few inches, then took a left for 12" and went back down. I couldn't find a chip so went to the dealer. He pointed one out at the very base of the windshield.

Had that one replaced (@ $250 deductible) and two weeks later a semi kicked up a rock that put a chip int he middle of the windshield. After much cussing, decided to try to get the chip repaired. Waited too long, cold morning, warm defrost, and what do you know, I got a crack all the way across the windshield. I decided it will stay there until spring. So I will have $500 invested in windsheilds, money that could buy a couple of tires and wheels

 

Just great.....I had my windsheild crack too. Right in the middle, it went up about 3 inches then split in two different directions. One right, one left. Both to the edge of the defroster vents. WTF. I have read all three pages of this thread. Did we all have damage to the middle windsheild at the bottom, that we could not see?

 

If this is the case, would that be considered a manufacturer's defect? If it's underneath the seal then it doesn't seem likely that it was caused by a rock from the road. Or wouldn't it matter?

 

The manufacturers defect is they didn't put a rubber seal or gasket around the out side edge of the glass. Having the windsheild as upright as it is , it's gonna get hit head-on more, the least they coulda done was put a simple rubber seal all the way around so the edges were somewhat protected. To tell you the truth, if you get hit anywhere close to those edges it's gonna run.

 

Same thing happened to me. This summer, I accidentally left the top open during a bit of rain. I ran out, closed it and turned the heater on to dry out the interior. About 1 hour later, I turned it off and backed the Jeep out of the driveway. From the driveway's gravel vibration, the windshield cracked from the bottom up about 6 inches and then right for another 8 inches. I guess it must have been the heat from the defroster that made the windshield seal or something loosened and the glass cracked at the slightest bump. Only thing I know is I sure as hell can't try to find out if the dealership will guarantee it, an 18-wheeler threw a rock in the glass, definitively ruining my chances of getting a free windshield.

I guess there definitely is a problem with the windshield.

I have an '07 JK.

 

Oh come on! Everybody is acting like we all had the same thing happen and its each all our fault. I just can't believe all of us had the same crack on the windsheild and the crack was caused by a rock chip or damage that occured in the same exact place and then we used our defrosters and we all increased the crack in the same manner???!!! I bet all of our cracks look like this. (That was supposed to be funny.)

 

ya, that is not from a rock chip. looks to me like there is preassure being put on the bottom edge of the glass causing a crack to run from there. Design flaw i bet.

 

Ours did this last winter while sitting in the backup on I-70 during that blizzard in Colorado.

Dealer did the pen test and replaced it under warranty.

Now, if I'm stopped I'll turn the temp knob to 2-3 o'clock to lower the temp a bit.

(White arrow is a chip caused by a rock salt kicked up a line hugger.)