[Masteryota]

Testing each leg should result in resistance one way, and open the opposite way. As long as the resistances are close, then I would give it a passing grade. Differences in resistance can signal a breakdown in a diode, or it will read both ways. I don't know what the resistance values are for all regulators, but the above should get you pretty close during diagnosis.

As for the power supply, either one would be ok, but running off the power block would be neater, IMO. I would convert to LED lights, low draw, low heat, and vibration resistant, guaranteed not to over draw your charging system.