I've been working on getting a Celica up and running after a couple years of laying mostly idle, it's been dry-stored for most of it.
The biggest issue I have right now is that the system is not charging the battery at all, I've done some basic testing with a multimeter and to my (limited!) knowledge I think the problem is within the alternator assembly. The vehicle is specifically a 1991 Toyota Celica GTR 4WS with a 3SGE engine.
At idle, I have battery voltage, around 12.6V but dropping gradually when running. The battery is brand new as it needed a new one (note that it did have a bad battery in it for a long time which didn't hold a charge) From the Battery positive post on the alternator to the Negative terminal on the battery, I'm reading the same voltage as the battery.
I think I've done voltage drop tests correctly on the alternator wiring (positive to positive / negative to ground using the voltmeter?) and the values were very small, only 0.01-0.02V at most.
I don't notice any strange noises or smell from the alternator, I just want to get some opinions on what it could be. I've posted pictures at the link below on what it looks like and what's I've done, any help is appreciated! What I think may have happened is that because it was using a very bad battery for a long time - we might start it up every few weeks, that the alternator brushings (not sure if that's the correct term) may have worn down by trying to charge it too much
I have some basic knowledge of circuitry and electrical systems so feel free to comment and help a guy out!
Link to Imgur album of the alternator -> https://imgur.com/a/JAZguTG