1) A meter across the battery terminals, while running, should tell you. In Volts DC, you should be getting close to +14 volts.

2)If not, switch to Volts AC and you should have less than 1 volt.

If #1 and #2 are not satisfactory........... change the alternator. The rectifying diodes are fried (and probably the regulator as well).

If only #1 is not satisfactory..........change just the regulator.

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )