It sounds like you had your meter in the amp setting, which would make your meter a short across the battery.

Ensure the setting is DC Volts and about 20VDC range. 12VDC=engine off; 13+VDC=engine running.

Then place the setting to AC Volts and check across the battery. Should be less than ! volt AC.

If DC volts are low......regulator.
If AC volts are high........diodes

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )