I tend to break these into sections, and they are really, dead nuts simple.
1...The alternator, "does it work"
2...The regulator, "does it work?
3...The field wiring, aka from the "run" line to the regulator, and to one of the two bruses, from the VR to the alternator remaining field
4...The charge wire, ammeter circuit, is it open, resistive, etc
First determine if the alternator can charge, and if the charge wire is OK
To do that test in two ways.
1....remove the green wire from the alternator field, and ground that alernator terminal. Turn on the key. Whatever the "run" line is, the blue at the alternator field should be the same. Start the engine, monitor battery voltage with your meter and watch the ammeter, unless you've bypassed it. The ammeter should show a charge and the meter on the battery should rise in voltage. Do not rev it up too high and keep the voltage below 16V.
2....If that is bad, recheck with your voltmeter on the alternator output stud. If the voltage is way high, the charge circuit is open. If it is low, below 13V it is not charging. Remove and inspect the alternator. Could be worn brushes, or something more serious
3...If the test above DOES show a charge, now we need to check the regulator wiring. Unplug the VR, and device a method, machine screws, etc, to jumper the two VR connector terminals. This time, reconnect the green to the alternator field, and remove the blue wire. Ground that field terminal. Again with your meter on the battery, it should charge.
4...If this is good, remove the VR, clean / scrape the mounting holes, and around the mounting holes on the firewall. The VR MUST be grounded. Inspect the VR connector for corrosion, as well as the male pins on the VR. "Work" the connector in/ out a few times to scrub the terminals. If you can buy a .17 caliber (same as BB/ pellets) bristle brush, that will clean those type of connectors, including the flat rubber trailer connectors.
If remounting the VR, and you are sure the terminals are clean, does not charge, replace the VR
