So I have been slowly gaining confidence in my FSM and I started trying to troubleshoot why my rear defroster doesn't seem to work. I did all the troubleshooting steps and found that I am getting essentially 0 ohms across the rear glass (good), and I'm getting 12V at the connectors at the bottom (near the seats). Here's where I think I've got the problem. First, those connectors are crap. They give very loose connections to the tabs on the struts. Second, I am not getting 12V at the TOP of the struts (at the glass). I'm assuming that the design uses the struts themselves as conduits. I took some fine sandpaper and took the oxidation off the tabs (no way to do it in the plugs that I could tell) but still didn't get 12V at the top. I started messing with the struts and noticed that they screw in to the post connectors at the top and there is a little star washer that goes between the strut and the tab for the connector at the top. As I was screwing/unscrewing the struts, I was getting sparks. I took the struts off at the top and sanded the connections as best as possible but after putting it all back together, 0V at the glass. I noticed also that the star washer wasn't touching the threaded part of the strut.

Where does that voltage come in? On the post (silver part) or the strut body (black part)? How can I get this connection to be better than it is? How do I make the connectors a tighter fit on the tabs? I also noticed that the stranded wire that connects to the defroster element seems to be only connected by a couple of strands anymore. What's the best way to repair this?

 

Silver-solder repair of the braided lead etc isn't I believe covered in an '84 FSM. It is in later years but I believe it's just done with 3% silver and you can maybe buy appropriate leads. They used to be available and I believe I've seen it done with just wire. There is very likely NOW conductive epoxies that might well do better.

GOOGLE might offer up some help. Try "silver-solder defroster grid".

Your 0V might have been because the defogger "timed out" - I don't know exactly how you did the task so it's maybe not obvious.

I can send you the later FSM info but it seems you understand and just have to sort out the best way to proceed.

 

It's been many years since I addressed this issue with my 1985, but what I discovered was that my strut was not conducting power to the grid. I replaced the strut and everything was fine.

I purchased the car new and never used/checked the rear window defogger. A few years later I happened to try it and it did not work so I started troubleshooting. That's when I discovered that I had power to the strut, but none coming out to the grid. I also recall that the strut was very warm to the touch. I concluded that the strut was acting as a resistor and reducing the current that made it through the strut. GM may even have issued a bulletin on it, because my sister worked for a dealer at the time and she would send me every bulletin when they came out.

Good luck... GUSTO

 

Seems like the problem I had with my 86's not working was the strut too.

 

Thanks for the advice. I'll be ordering new struts post haste. =0)