window defrost grid

[Dave WM]

I have about 2k ohm resistance and no heat being generated (a few ma at best flow). Don't like the idea of a grid replacement kit that sticks on, and the minute amounts of conductive repair kit only allow for a very limited fix. With my VOM is seems like most of the grids are simply non conductive even though they seem intact.

I was thinking of using an air brush and masking tape to mask off and reapply some kind of conductive paint. see link for a decent amount of paint to work with.

https://www.amazon.com/Caswell-Copper-Conductive-Paint-4oz/dp/B00A6FO6G8/ref=sr_1_1?ie=UTF8&qid=1536694226&sr=8-1&keywords=caswell+copper+conductive+paint

I was hoping that copper head gasket seal may have had real copper in it but from what I have read it is color only, non conductive.

 

[Dave WM]

oh and I have some spray graphite I used for dag on old CRT's I may try and see how fine a line I can make on some plate glass just to see how it would work (spray on covering with masked off lines).

[David F]

Good luck...hope you figure something out.  I'm the same boat with my car and the rear defroster is the only non-functioning part on my '72.

[240dkw]

you could try this https://www.amazon.com/Products-0768-Copper-Through-Primer/dp/B007IU78HS/ref=sr_1_1?ie=UTF8&qid=1536705089&sr=8-1&keywords=weld+through+primer
it drys with a copper colour

[Patcon]

The Caswell product is waterbased and I see problems with cleaning the glass or condensate on the interior surface. You really need to find a solvent based product

Maybe one of these:

https://www.midwesttech.com/Electrolube-scp03b-scp-silver-conductive-paint-3g/?gclid=Cj0KCQjwz93cBRCrARIsAEFbWsh5v55IRJDBayNKbkamMSkGJajY7W_J1Lpt9YL1ZX0Vm0m6nmgewXsaAkE5EALw_wcB

https://www.etsy.com/listing/519528043/silver-conductive-paint-scp?gpla=1&gao=1&&utm_source=google&utm_medium=cpc&utm_campaign=shopping_us_b-electronics_and_accessories-other&utm_custom1=b66cd0c9-ee2b-42c1-98c1-4d27634cbc4f&gclid=Cj0KCQjwz93cBRCrARIsAEFbWsgTmeVGslyQpamHc6pYAtTZE6mN0NNWoSss2Gc1j9cY4iEpD2s0GgMaAjsIEALw_wcB

https://www.google.com/shopping/product/9674429714092994981?q=conductive+spray+paint&biw=1366&bih=632&prds=paur:ClkAsKraX2z4DA6QMUsuu51_rStj--GYT7m-VzJZJ1XIXN_UWQhoRrAg2cgiQO-GbvEgCFtJHnHcYJ2_kO5PqO5H2R4AbNlQU5erAjTfs1XHuRffBO6NM-KwwhIZAFPVH71QOWWvgdHBi0RNSblIutnZs4kC_w&sa=X&ved=0ahUKEwj1mOS2hrTdAhUM0lMKHZoODagQ8wIIgwM

[Zed Head]

I ended up using a fan wired in to the defrost circuit.  It's a 20 amp circuit.  A cheap Oreilly Auto fan got me by the first few years until I got all of my leaks fixed and things finally dried out completely.

Edited September 11, 2018 by Zed Head

[Dave WM]

some good looking products on those links. I just tried it out on a piece of plate glass, approx. the width of the hatch with some of my "slip plate graphite coating". I am sure its not a good choice but since I had it on hand figured why not. If nothing else it will be one of the many products to test. should be interesting to see the resistance reading. Left a nice black line. The masking was pretty easy, with the grid as a guide I suspect it will be very easy. have to let it dry, so maybe a few hours from now I can give a report back. should be able to compute the amount of resistance of a single line, the multiply by number of lines to come up with a  resistance reading to do some current/wattage read out. have no idea of what it should be but figure 10-20 watt would be good, so lets make it easy 12 watts would be 1 amp at 12v. guessing they are about 1" apart and say about 2 feet so about 25 grid lines. I=E/R so 1amp=12v/12ohms, 12*25=300 ohms per line (300ohm in P would be 12ohms total).

so as a target assuming I have the right number of lines, I am shooting for 300-150 ohms per line. that would give me 12-24 total watts. Of course I have no idea if the required wattage is right. Suppose I could go measure the current thru another car with a working defrost, just to see if I am in the ball park

Think I did that right.

 

[Dave WM]

big fail #1 about 2 meg over about 2 feet, clearly not conductive enough. Guess I should have figured that, don't think graphite is a very good conductor, couple that with thin line an very thin deposit...

I will look into those other products. I was encouraged by how nice a line I was able to get. I googled to see if anyone had tried to reproduce an entire grid, but could only find the small fixes for breaks OR the complete grid that is solid looking copper strips that have to connected in series to prevent too much current.

Seems like the best way IF a good conductor can be found, would be to have a stencil made up, position it and then shoot the whole thing in one pass.

Edited September 11, 2018 by Dave WM

[Patcon]

4 minutes ago, Dave WM said:

big fail #1 about 2 meg over about 2 feet, clearly not conductive enough. Guess I should have figured that, don't think graphite is a very good conductor, couple that with thin line an very thin deposit...

I will look into those other products.

Very interesting. It would be nice to find a product that performed well at this. I suspect many older pieces of glass could use some attention like this

[Dave WM]

indeed it really bugs me when things don't work as they should.

[Dave WM]

think I will try this one, like the idea of brushing on to build up a thicker layer quicker, and used for track repair (assuming that means PC board tracks) would have to be very conductive.

https://www.etsy.com/listing/519528043/silver-conductive-paint-scp?gpla=1&gao=1&&utm_source=google&utm_medium=cpc&utm_campaign=shopping_us_b-electronics_and_accessories-other&utm_custom1=b66cd0c9-ee2b-42c1-98c1-4d27634cbc4f&gclid=Cj0KCQjwz93cBRCrARIsAEFbWsgTmeVGslyQpamHc6pYAtTZE6mN0NNWoSss2Gc1j9cY4iEpD2s0GgMaAjsIEALw_wcB

 

oops, yikes think its like 15gm, going to have to do some more research.

Edited September 12, 2018 by Dave WM

[Patcon]

Yeah, I didn't look that close. I did a search for conductive paint to find those. You may just have to look farther back in the search results. Might need to specify aerosol