[gto4ben]

A clamp-on DC ammeter would be more helpful in tracking down a parasitic current leak. Since it appears you don't have one, use the ohmmeter setting.
Assuming the alternation is the original 10DN type, disconnect all the cables connected to the BAT terminal and disconnect the F-R connector. With the ohmeter positive lead on the BAT connector and the Negative lead to alternator ground, see if the reading is > 100KΩ. (Note that there is a 0.5uF capacitor in the alternator and it may take some time to stabilize.) If lower, one of the alternator diodes or capacitor is leaky.

With the BAT terminal still cleared off cables and the F-R connector removed, set the ohmmeter positive probe on the R-terminal and the negative probe to alternator ground. This checks the diode powering the regulator field solenoid. See if the reading is > 100KΩ.