[Chrysler kid]

The alternator functions separately from the cars computer. You just need to stop power from getting to the regulator from the battery on the plug.

Alternators can be tested independently at part stores to simulate all voltage ranges. All they do is supply it with a constant power source and vary the load to the regulator.

While helpful the description of the computer controlling the alternator is incorrect, voltage to the regulator does that

The simplest way would be to wire a switch into the alternator harness to disconnect the feed signal to the voltage regulator.