1972 dart alternator pulley shaft question

moparjon said
sorry to ask , but , exactly how do i do that ?

With engine running...
Measure from battery ground to alternator out put and then measure from battery ground to battery positive terminal.

Another way is to measure between battery positive and the alternator post. This should show very low voltage like 0.5v or less

When comparing between battery 12 volts and alternator voltage 12.5v the difference is the voltage drop 0.5v (the numbers are for example only)