Leaving for work this morning the windows were fogged so I put on the front and rear window defroster. Light rain with temp in the upper 40's. Drove 5 miles and while sitting in the parking lot the left rear window shattered! Nothing hit it so I'm guessing the defroster element wires may have something to do with it. I noticed the leads at the bottom of both rear windows look discolored, almost burned. I covered both sides with duct tape to hold it together until I can get it repaired. The auto glass shop quoted about $250 for a new window and said they see this happen often.
The Ford manual says "the rear window defroster will turn off after a predetermined amount of time, if a low battery condition is detected, or the ignition is tuned off" Maybe mine isn't turning off and overheating the element and glass?
I'll stop by the dealer next week and see what they have to say.