[RichardJ]

To check the ground connections use the volt meter with the engine running. Check the voltage from battery negative post to engine, negative post to frame and negative post to regulator frame. You should get 0.0volts or at most a few tenths. A bad ground or an open ground will read several volts or higher.

The wire from the ignition switch can be checked with your volt meter. Pull the plug off the voltage regulator and with key ON, engine OFF there should be battery voltage on the pin #4 wire in the plug.

It is not really a good idea to solve an unknown problem by introducing a new variable such as a new charging system. You may end up chasing two problems instead of one problem.

The existing wire from Alt to Battery serves as the shunt for the factory Ammeter. It is effectively, part of the Ammeter. Changing its length or gauge will change the Ammeter.