Alternator not charging

Mattax said
Read this so you have a good idea how the circuit works.
Understanding Charging Systems with Ammeter

On yours, the blue wire feeds the alternator's field and the green wire controls the connection to ground completing the circuit. So the blue will connect with voltsage regulator and the ignition 'run' side junction on the ballast resistor. This is how the regulator knows the system voltage. It regulates by opening and closing the circuit's connection to ground.

Field is another name for the electomagnet that spins. The windings create an magnetic field when powered up.

Here's a general diagram of the later charging systems like yours.