My windshield did develope a crack a couple weeks ago, but I haven’t used a shade at all this year. I’m just wondering about the potential of trapped heat between the glass and the sunshade.
Extra point:
My son-in-law said “Yeah, those unibody vehicles”. Does unibody construction add extra stress to a windshield? I own a Honda Ridgline. I can see how it might.
Peace,
mangeorge
The sunshade does not trap heat between the shand and the windshield (at least it shouldn’t). That would do no good, since the heat would then be already inside the car, warming it up. A proper sunshade will be made of white or silverly material, to reflect the sunlight right back through the windshield into the outside air, rather than letting it be absorbed iinside the car.
I saw a case where an outside reflective material was put on the inside of a double pane window and the window rather soon thereafter exploded, from something.
What happens, sun shade or not, is that a temperature change can exploit a minor flaw in the windshield that you might not even be aware of. A little rock chip that hasn’t even caused a star/crack. Maybe you didn’t even know that a rock had chipped the window.
On a very hot day the small flaw may run into a long crack.
Once I went to wash my car and sprayed water on the outside of the windshield. A small chip in the bottom of the windshield decided to run and crack all the way accross the glass. I could hear it and watched it ruin the whole damn thing. Quite impressive.
On a related note to the second part of your question about uni-body cars. You may get a ticket or a warning from a cop for having too long of a crack in the windshield. You may think that this has to do with vision obstruction. Actually the strength of the windshield is important in a roll-over accident. A cracked windshield will let the cab of the vehicle crush easier. Integrity of the windshield is engineered into the roll-over results.
Hard to say. I don’t think one of those shades can greatly change the temperatures around the glass, or more to the point cause there to be extreme or unusual temperatures or rates of change of temperature. But the way glass cracks once it is chipped is a hard thing to predict. Perhaps the right chip could make a windshield crack when somebody got into the car, or when the sun came out, or when it rained, but you wouldn’t consider those events the problem.
I don’t think your experience argues against using the shades, though.
I think t-bonham’s point is correct and relevant.
I never used the sunshade, I was wondering if one could conceivably cause a crack. I placed in in the windshield this morning and when I left work, true to what others have said, it wasn’t hot between the shade and the glass. Something else obviously caused the crack.
Which is part of why I asked about the unibody possibility. I forgot to ask the glass technician, but my son-in-law does custom body work (low riders and “gangsta” cars) and knows what he’s talking about.
Thanks for the replies
mangeorge
As has been said, a rock chip (sometimes so tiny they can barely be seen) can become a great big long honkin crack.
The test the factory has me use, is run a ball point pen along the crack. If the crack was caused by a rock chip, the pen point will get stuck.