Solder on rear glass good or bad

Soldering it won’t conduct as well as it should. They make a special conductive epoxy for this:

Back Window Defogger Electrically Conductive, Silver Epoxy Adhesive Repair Kit 2.5 Grams https://a.co/d/0Ash8Qj

It probably works better than the stuff you were using.

Solder is WAY more conductive than conductive epoxy, but it’s probably not a great idea to expose the window to those temperatures.

3Dogs

Solder is WAY more conductive than conductive epoxy, but it’s probably not a great idea to expose the window to those temperatures.

I don’t think that’s true at high current

Sulley

Soldering it won’t conduct as well as it should. They make a special conductive epoxy for this:

Back Window Defogger Electrically Conductive, Silver Epoxy Adhesive Repair Kit 2.5 Grams https://a.co/d/0Ash8Qj

It probably works better than the stuff you were using.

I guess I'll try this one as well. I figured the stuff I used would work since it's also "Electrically Conductive Rear Window Defogger Tab Adhesive" but I guess some are created more equal than others. Thanks for the link @Sulley I'll keep y'all updated on this malarkey.
I like soldering things but the glass does make me nervous. Although it looks like "the internet" says tempered glass begins liquefying at the lowest ~590C / 1100F and I can easily melt solder at less than half that. My concern is more around the adhesive used to keep the defroster attached to the glass.

Sulley

I don’t think that’s true at high current

It’s absolutely true.
One-part silver-filled epoxy has resistivity “less than” .001 Ω-cm (or 1000 µΩ-cm)
(from here: https://www.masterbond.com/properti...device=c&adposition=&keyword=conductive epoxy)

Typical lead-free solder has resistivity of .140 µΩ-m (or 14µΩ-cm)
(from here: https://invacu.com/solder-alloys)

So, solder has 71 times better conductivity than conductive epoxy. If anything, the epoxy will be much worse at high currents, because it will heat up and tend to separate the conductive grains.

Also just saw this review on that product page:

Seems like everyone has their own experience with this stuff. I can't lie I'm kinda just curious about using solder. I'll report back :)

OK I did it. It's not a pretty solder, but I tested continuity and it was good, then I reattached the connector and tested functionality and it heated up nicely with no visual change to the connection, so I'm happy.
The solder did NOT want to connect to the copper (?) on the window, so as soon as I got a blob to affix, I left it. Probably didn't help that it was kinda upside down ... and I probably could have done some better prep, but I didn't want to sand too much, I'm not sure how thin that stuff is. You can see that I tried multiple points of attachment around the tab until I got somewhere that actually worked. Who knows. But so far so good, hopefully it stays together!

magicrobots

OK I did it. It's not a pretty solder, but I tested continuity and it was good, then I reattached the connector and tested functionality and it heated up nicely with no visual change to the connection, so I'm happy.
The solder did NOT want to connect to the copper (?) on the window, so as soon as I got a blob to affix, I left it. Probably didn't help that it was kinda upside down ... and I probably could have done some better prep, but I didn't want to sand too much, I'm not sure how thin that stuff is. You can see that I tried multiple points of attachment around the tab until I got somewhere that actually worked. Who knows. But so far so good, hopefully it stays together!

Glad it worked!
I would reinforce the connector-to-glass area with JB weld.

3Dogs

Glad it worked!
I would reinforce the connector-to-glass area with JB weld.

Thanks! So far so good - the connector is actually really solidly epoxied to the glass. I tried to use one of those supposedly conductive epoxies specifically for this purpose, and it holds the connector on nice and tight but doesn't conduct electricity. LOLZ Maybe I got a dud batch or it was manufactured in 1983 or something.