Do not use front defrost for extended periods- cracks windshield

From my NHTSB report- Friday January 12, 2018, drove vehicle 3.5 hours on highway during period of declining temperatures- 34 to 29 Fahrenheit, with snow beginning hour 2.5. Operated front defrost continuously for entire 3.5 hour trip with cabin temp between 72 and 75F. Made 2 stops, 10 minutes each- one at 1.5 hours and one at 3 hours. Parked overnight in home garage at end of trip. Air temp declined to 19F overnight. Backed car out of garage in morning and windshield cracked at centerline of front defrost vent. Crack has continued to expand to points almost exactly 5 inches beyond each end of defrost vent, then stopped expanding. Passenger side (right side) crack is aligned exactly with centerline of defrost vent. At point 5" outboard of vent, passenger side crack turns down and extends to bottom edge of windshield. Driver (left side) crack is parallel to vent on line 3" below vent, then turns up, crosses vent, and parallels vent 3" above vent to termination of crack at 5" outboard of vent. Nothing impacted windshield during trip and windshield was not cracked at end of trip. Engineering defect- inadequate glass strength- unable to use defroster for extended periods. Crack created by stress from localized thermal expansion- aligned with heat source of defroster vent at lower middle region of windshield. This is first extended use of defroster in car- purchased May 2018. Currently has 21,800 miles.

 

It was not cracked when it went into the garage. It occurred as the window cooled over night.

 

Yes, May 2017. My mind is already committed to 2018, I guess. I'm not sure if there is a stress point in the glass caused by the installation procedure, of it there was a defect in this particular glass, or if the glass expansion caused by the not particularly hot 72-75 degree defroster heat simply exceeded the performance specification of the glass. I initially turned the defrost off once the interior of the glass was cleared, but it fogged up again almost immediately. I then left it on for the duration of the trip. I didn't want to be distracted by constantly turning it on and off and having my vision obscured when the defrost was off. Weather conditions were as warm as it can be for snow to occur- low 30s, but also very high humidity. So, conducive for fogging the window. And In my 33+ years of driving, with approximately 1 million miles driven, I've not had a situation where operating the defroster broke a windshield. The fact that both ends of the crack terminate 5 inches from the ends of the defrost vent indicate to me that the temperature gradient was a factor- the glass was compromised to the location where the temperature declined due to the distance from the heat source. Beyond that 5", the glass wasn't warm enough to fail. This should be a situation that can be reproduced by Toyota engineers- with their own windshield, not mine!

 

I've taken it to 2 dealerships in central Ohio and they told me that Toyota will not cover windshields under warranty. I have called Toyota's customer service number and was told that Toyota does not replace windshields under warranty. Which, in this case, is absurd.

 

Two Eco

 

I have not looked, since they have a fundamental obligation to make it right. I operated factory-installed equipment in the manner in which it was intended to be operated- for my safe operation of the vehicle- and at far less than its maximum capacity even, and the proper use of that equipment damaged an adjacent part of the vehicle. This needs to be resolved by Toyota. Period.

 

Prodigyplace- your experience did not relate to heating and cooling of the glass, though. Heat appears to be the primary factor in this windshield failure. Sounds like your wife had quite an experience. I'm glad she's ok.