Re: Spontaneous Windshield Breakage?!?

[William Elliott <William.Elliott@mail.mei.com>]

>>>an opposite effect: if you drove your car for a while with the A/C
set to
>>>low temperature and then left the car in a sunny spot, the windshield
could
>>>get rapidly heated and break from the stress.

>>Good point. I never thought of that before. Thinking of the my
>>windshield being glued to the car body and the fact that the car is
>>black which attracts heat makes it even worse.
>>I conclude: No cool air on windscreen.

>>BTW, isn't it even more critical in winter to scrape the ice off the
>>windscreen and then toasting it by blowing hot air?

>From my understanding, this is not overly critical because
the cracking comes from the high rate of thermal transfer.
Assuming a normal automotive heater, the coolant warms
slowly enough to gradually heat the windshield. (OTOH, An air
conditioner, working independently of coolant temps, can
manage a great temp change in seconds.)

Related point:  Everybody remembers Corvairs as having
poor heaters.  What people generally don't remember is that
in 1960, Corvairs got no heat from the engine, but instead used
a gasoline-fired heater in the trunk.  (Of S/W manufacture... 
almost identical to the optional VW gas heaters of the same 
period.)  These heaters (optionally available in some later
years as well) could blast out air in excess of 150F
in about 2 minutes.  Quite different from the "hot air"
Corvair units which only offer 150F air in the summer. ;-)

Owners quickly learned that windshields would routinely
break on cold winter mornings if the defroster were 
initially turned on.  Most used only the "heat" setting.

What I've never figured out are those guys who pour
hot water on their windows for de-icing.  (I know we're
supposed to have this thread in the winter months!)

Bill Elliott
Lake Mills, WI
UrQ and Corvairs