I have had 3 windshields put in my 03 Legacy GT in the past year. Every time a new one gets installed it cracks as soon as I hit the heated Windshield button for the wipers.

Any thoughts?? I haven't paid a nickle for any of them but its getting annoying. I guess I could stop pushing the button.

Though glass expands very little under heating it does expand. I think there is a sharp spot of metal where the glass expands against and breaks. I assume your window does not shatter into pieces but just a single or double crack. The location where this is on the windowframe might be the source of the breaking.

 

When they replaced my windscreen they had put ducktape from the roof onto the windscreen. This stayed on for 1 day. It was to prevent the window sinking down (downwards to the end of the frame at the wipers), when the glue hardens.

Maybe your windscreen sunk to the lowest place of the frame. At the moment you switch on the heater it wants to expand there the most but there is no space. It probably can not push the rest of the windscreen upwards and it cracks to release the mechanical stress.

Does it crack in the same place each time?

 

I had a MY01 Outback Wagon crack starting at the bottom and working up to under the center of the wiper blade under the driver's side. I took it back to the dealer under warranty but they claimed it was a stone strike so I was waiting until inspection to spend the money on replacing it. About 2 months later the SAME exact thing happend on the passenger side. Both were almost 1/4 inch within the same spot on either side.

 

Back to the dealer, figuring I had a chance at now getting it fix, and the service manager again insisted the same thing, stone strike. The mechanic even argued my side. I went to the owner and pleaded my case and they replaced the glass. The mechanic told me it looked like a bad install and they were possible stress breaks from either incorrect positioning of the original glass or a shock to it before the install.

Thanks for the replies, they both make sense and to be honest I don't know exactly where the crack was before. It was cracked all over the bottom. I will be there when they put the next one in to inspect the pinchweld and also for anything that it may rest on if it were to slide down.