headlights not working

Unhook the battery, and no do NOT turn anything on. What we are trying to see, here, is if the "path" from the alternator to the battery is OK, and "I'd guess" it is not. Wiggling the bulkhead connector may give you a clue if the trouble is in there.

So with the alternator black wire (nut and stud) disconnected, connect your ohmeter to that black wire/ eyelet. Then connect the other meter lead to the big stud in the starter relay, or to the battery positive post. AGAIN the battery ground MUST be disconnected.

You are hoping for a very low ohm reading, the lower the better.

Another thing you could do is run the engine at fast idle with everything wired up "normal" and clip your meter to the alternator stud and ground. Wiggle the bulkhead connector and see if you can hear arcing, smell or see smoke, or see the meter reading fluctuate.