Haynes wiring diagram doesn't show any exotic relays or control units managing the charging system. So I am pretty sure the regulator is the culprit.
As far as the radiator, it had MB coolant. Broke at the plastic hose neck, like they all do.
Starting the dismantling process in anticipation of the alternator showing up at the end of the week. I hope to be up and running by Monday.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car