They are mis-applying the science. If you were to pour hot water
on a very chilled windshield, likely you'd crack it where there are chips.
It
happens when volks are having their cars worked on and already
have a chip or small/short crack. The shop people pull the vehicle
into a very warm garage, out of very cold weather, and boing....
the crack-runner appears. Happened to a Nissan Pathfinder of mine
once long ago. The molecules change size quickly and the weak
spot is exposed.

bob

On Fri, Dec 11, 2009 at 6:36 PM, Rob <becida@comcast.net> wrote:

> At  12/11/2009 02:08 PM,Matthew wrote:
>
>  it was around zero degrees f here this week. A coworker claims that
>> if i use my rear defrost it will break the rear window? Before i
>> call Tom and Ray, will someone chime in??  it seems a bit improbable.
>>
>> thanks
>> Skeptic Matt
>>
>
>
>