I'm sorry, I had thought about adding this to my previous post about my electrical issues with this rig (turned out to be the wire at the fusible link box). But decided the symptoms were different enough that I would start a new post.....so I forgot some of that crucial background information. Like, it's an '84 brat, stock EA81. AFAIK the entire electrical system is almost completely stock. If you've seen pics of my brat, don't be fooled, only the decals say turbo, it never was.
Another piece of information from the other thread that I should have re-iterated. My brat is not stored at my home. It's at a friend's shop, about 25 miles from my house, and not in a direction that is on the way to anywhere....so diagnosing problems are a bit difficult. Closest auto parts store to the shop is about 18 miles one way.
Also, as soon as I finish building the 5-speed, it's getting an EJ. So bandaid fixes are preferred for now.
Alright, all that said. Let me simplify the symptoms a bit:
All of the symptoms all day match up with a failed battery. Frozen, or just plain dead. Not accepting a charge. Basically, I'm running off the alternator.
BUT, early in the day, I swapped batteries with a buddy's jeep. His battery had a great charge, which allowed my rig to restart when necessary. After about 4 hours in his Jeep, my old battery had been charged very well. It started the jeep again when we got back to the trailers, and when we swapped it back in the brat, it easily restarted. So, it's not the battery.
Also, with the good battery in the brat, the volt gauge still jumped all over the place.
In my experience, a car with a good alternator/regulator, but with a completely failed battery, will show some pretty crazy voltage variation related to the engine speed.
With the engine running, it's the same symptoms that I noticed when that terminal at the fusible links corroded. Except, when that happened, and the engine was turned off, jumper cables to the battery terminals didn't help.
It's like there's a diode in the system, allowing the battery to discharge, but not charge.
Here's the only pic of the brat from the day...checking the connections while I wait for a jeep to turn around and come give me a jump start to get another run at that hill: