Electrical Help

My buddy has a '63 Dodge 440 with electrical issues. He believes he keeps "blowing" voltage regulators when he turns on the headlamps. Daytime driving he thinks it's all good.

He's replaced Voltage Regulators ~5 times that I am aware of (with both mechanical & electronic style). The alternator was replaced 2 years ago (O'Reillys).

Today the engine was warmed up and I made some voltage readings. Engine off the battery voltage was 12.5V. Engine idling in PARK battery was 12.25V, Alternator stud was 11.9ish Volts & the blue wire on the Voltage Regulator was 11.7ish Volts. Idling up the engine did not change the readings significantly.

He's got another alternator that will be going on tomorrow. But we're unsure where to begin. How do we know if a VR is "blown". Wouldn't a bad VR eventually kill (or boil) the battery? Wouldn't the alternator make the battery voltage increase, to 14V, when the car is running?

I'm at a loss.