Alternator Question

1990 V6 Runner - 180k miles.

Few days ago lights on dash started coming on at the same time, battery dying, checked batt, good, looked at alternator and the electrical connection that looks like a bolt sticking out of it was fried and the connection had become loose because of it. Put on new alternator because I didn't know if I could just replace the bolt.

The lights don't come on anymore on the dash (I think that was the loose connection) but the battery doesn't want to charge. It works for a little while, probably three or four individual drives at least 10 miles, but slowly begins to lower and lower until won't start next time.

Okay, now here's my question. Is that bolt connection on the alternator the output of it where I check the voltage and amperage? It seems like it is always the same as the battery voltage drop...

That large stud IS the alt output to the batt.

Alt should put out ~13.8-14.2 V when eng is running (measured at bolt or batt pos (+) terminal).
Batt will be 12 V or so when eng is off.

~13.8-14.2 V relative to chassis ground

I think I'm going to pull it and bench test it tommorrow. The voltage output is always identical to the battery, at idle, at 2000rpm, off, which makes me think that it isn't outputting a voltage at all and the voltage I am reading is coming from the batt. Is this the right way of thinking about this?

Okay, had the "new" alternator bench tested, it was the problem, so they gave me a replacement, had them check it before I left and it worked. Put it on and replaced part of the big wire going to it because it was pretty corroded and now everything seems to be working just fine. Hopefully it stays that way. I appreciate all the help everyone has given me on this! thanks!