How hot should the rear defrost grid get?

[Pyral]

I used a permatex paint kit to repair the painted conductive lines that make up the defrost for the rear glass.

I was checking that voltage was flowing through the lines when my hand brushed up against the repair paint and it was so hot that it hurt. I got out a kitchen thermometer and tried to measure how hot it was but I could only get a reading of 100F (probably not the right tool to measure my glass).

I can hold my hand against any other part of the grid without burning my hand, but when I touch the repair section it is too hot to touch. It technically fixed my issue with loss of continuity, but now I'm afraid that the higher temperatures of the repair area could crack my glass with thermal shock.

It should be noted that only my skin that is pushed up against the wire burns, the glass directly around it doesn't feel like its getting super hot.

How hot should the defrost grid get?
Should I worry if the grid is getting hot enough to burn me?

 

[Devbot]

I don't have an EXACT answer, but I'm pretty confident in saying that's a little too much. However I bet quite a few here would kill to have one that strong, myself included
Does it get that hot pretty quickly? Windows are fairly tough, but rear windshields are always pricey (about twice as much as a front typically) so it might behoove you to change it however that may be done. I only know people who've had thermal shock happen and never had it happen to me, so personally I'm a little torn on if it would be that big of an issue. I can see how it would and wouldn't be a problem - it's such a small, located area and if the glass doesn't get that hot then you should be fine; but at the same time, I feel like 100+ degrees and a sudden snowball or large, icy splash might not mix, or if it maybe warmed up too fast when iced over? But then again, if you live in the bay area... how cold are you really gonna see it get? I would imagine the glass gets just as hot in the California sun during the summer, when parked out of the shade and such
Thing is Permatex is a great company and I'm sure if you asked them directly they'd be able to offer at least some general information
PS: a laser thermometer is a fantastic tool to keep in the garage :thumb3:

 

[19963.4lsr5]

I used their product to glue my grid terminal on in my Saturn SL1. It worked great for one winter. Then the epoxy became non conductive which of coarse meant my rear defrost stopped working again.

My rear defrost on the 4Runner pulls 6a.


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[Pyral]

I read some amazon reviews where some people said the higher resistance of the paint could create hot spots, and a wider line was needed. One person said it broke their glass, if the review isn't fake I bet they had an extreme case of thermal shock.

 

[19963.4lsr5]

I read some amazon reviews where some people said the higher resistance of the paint could create hot spots, and a wider line was needed. One person said it broke their glass, if the review isn't fake I bet they had an extreme case of thermal shock.

Higher resistance is less current. I suspect that review.

My grid resistance is around 2.3-2.5 ohms.


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