Little question, biiig answer. Since there has been work done to the vehicle, there a re a few preliminaries that must be checked.
1) Make sure, by removing and cleaning, that you have a good ground from your alternator to the engine, and from the engine to the battery. Replace any corroded cables.
2) Make sure, by removing and cleaning and testing with voltmeter both resistance and voltage drop, that you have a good hot path back to the battery.
3) Make sure, see above, that all the pins of all connectors are straight, and make good tight contact, and there are no funky repairs to the wiring. Replace/repair wiring as needed. Only use solder on the connections, not solderless crimps. Crimps can be used if you then solder them and use shrink wrap.
4) Remove the regulator and make sure, see above, that all the contacts are clean and that they are there, not worn off.
5) Retest the system.
6) If the system does not charge properly, then replace the regulator. It is available in the aftermarket for about $40.00. I've gone through 3 on my 93 Ranger without replacing the alternator itself. It bolts on the back of the alternator with (maybe) torx screws (yay)