ALT gauge issues- clicks and pulses 69 DART. NEED HELP!!!

I didn't dl the videos. So what will pulse system voltage at few second intervals ? ... Mechanical voltage regulators. And the OEM system contains 2 of these. One for charging system and one for instrument voltage. There is a way to isolate and determine which is the culprit. Replacing both with modern solid state is typical.
( a vintage car clock pulses system voltage too but at closer to 3 minute intervals )