ok, here is the deal, there are two types of alternators and two different ways of making them work.
the first type has one field wire going to it, this is one side of the "field" the other side of the field is grounded to the alt case.
this type of alt/reg combination works by varing the volts TO the field.
the second type has two wires going to the alternator, one wire has 12VDC when the key is on (one side of the field).the other wire is tied to the voltage reg. in this system the voltage reg, varies the resistance to ground.
it is very important that you do not mix up the two, you need to know what you got.. as far as reg, wire harness, and alt.
its all about current flow through the field, you either vary the pos voltage going to it OR you regulate the current by inc/dec the resistance to ground.
i did not mention there is a battery lug , but that is a bigger gauge wire, it usually lands "indirectly" back to the battery. this is where the current flows to charge your battery.
do you have agood ohm/volt meter? there are several checks you can do.