Okay, just got done with some testing. After jumping it, my daughter drove the car 5 minutes to work, shut it down, and it sat for 5.5 hours. When I got there, the battery was at 12.3 volts. Low, but should still start, right? While cranking, though, the battery voltage dropped to 6. We jumped it with the jumpbox and once running, the battery posts measured at 12.8. Not great. We looked for voltage drop on the battery positive to the starter terminal from the battery negative to a bunch of places on the chassis and engine and didn't see anything amiss. Voltage between the top adjuster nut on the alternator to the starter terminal, however, was 13.8-14 volts. That's way more betterer! Voltage drop from that same place on the alternator to the battery is about 1.5 volts.
I don't know that I've ever had a vehicle that had a ground wire on the alternator before - everything I've ever messed with just grounded through the mounting bolts, but I guess if they're using rubber bushings, that wouldn't work. Also, I only found one rather thin, insulated wire coming off the bottom of the alternator and running to an attachment point sort of behind/under the alternator near the mounting bracket. Is that really all it needs? I'm contemplating using a much heavier gauge wire, putting some terminals on it, and going from the adjuster nut to the mounting bolt for the A/C compressor right above it.
Full points for the tip on the ground wire, thank you! While I had my head in there, I looked for the regulator and can definitely see where that's bolted in. the voltage at the alternator itself was pretty stable, though, so it's safe to assume that the regulator is doing okay at this point. The ground wire seemed to be fairly well secured, but I wasn't really able to get my hands - or my multimeter probes! - in there to test it directly.
Right now, we've got the battery on the 6A charger. After a few hours, we're going to take the charger off, let everything sit for about 30 minutes, and then watch the battery voltage during cranking again to see how far it dips. The battery is a cheap Everstart from Walmart which is mounted about three centimeters and a plastic shield away from the turbo and its exhaust, so I wouldn't be totally shocked (ha! get it?) to find that in addition to the grounding issue, the battery is also malfunctioning. Especially if we haven't been charging it correctly for a while now.
You know... When I first saw that car on FB back in Feb, I kind of figured that it was in pretty sorry shape since it had been listed that long and wasn't in your collection yet! I definitely wouldn't pay what he's asking - I can only imagine how much it's decayed in the last couple years - but I could see spending a couple bucks for it if there was enough to harvest before getting almost all my money back at the scrapyard. I might have been willing to get closer to that when I needed collision repair bits and a radiator and stuff - if that would have been compatible, even... I never got to the point of really looking hard at it - but since I've already got all that, its value to me is quite a bit less.
I've got to figure if you did round those bolts off, you're pretty screwed. I've replaced all my 12-point HF specials with 6-point Tektons for that reason.