All

My Question:
Does a new Voltage Regulator need to be broken in or do I have a bigger issue? I noticed that after it had been running for a bit (10 minutes), the idle voltage increased but still didn't reach a voltage level I was expecting from a good alternator/voltage regulator combo. Was 12.5V increasing to 12.9V after 10 minutes at idle and 13.48V above idle. I was expecting over 14V. Do I have a larger issue at hand? The new voltage regulator has increased the voltage observed while running, but not to the level I would have expected. Am I missing something?

Any/all thoughts are appreciated!


-----Related information which may or may not be helpful-----
Vehicle:
1978 300CD

Initial Symptom:
Car wouldn't start. Insufficient battery power even after running. Wouldn't have a sufficient charge to start the motor even after running around the block a few times ~10 miles.

Troubleshooting steps taken:
Jumpstart vehicle and test voltage at the battery. Voltage while running was below 12V. Suspect deficiency in alternator or voltage regulator. Removed and inspected Voltage Regulator. Spring loaded terminals were 7/16ths of an inch long (I read in another VR related post, if they're below 1/2in, you may want to replace the VR before replacing the Alternator).

Relevant History:
Battery is Sears Die Hard International approx 6 months old. Car has less than 300 miles since new Battery
Alternator was replaced 3 years 11.5 months ago. Car has approx 20,000 miles since rebuilt Bosch alternator/volt regulator.

Actions Performed:
Replaced Voltage Regulator, Jump Start, and Retest Voltage at battery terminal.

Findings:
Since I don't have a tachometer, I have to go by feel. Since I'm not an idiot (well... complete idiot at least) I ran the engine at idle and at a rev plateau above idle where the engine smoothes out (I'm guessing ~1000rpm). Anyway, here's what I got:

Idle Voltage At first: 12.25V to 12.45V bouncing
Revved Voltage At First: 13.48V steady
Idle Voltage after 10 Minutes: 12.9V steady
Revved Voltage after 10 Minutes: 13.48V steady

I was expecting to see over 14V when running (at least while revved) but when the Voltmeter hit 13.48V, it looked like it hit a wall. I didn't see any momentary spike above 13.48V when revving it up under any of the conditions I tried. I gave the engine as much as 1/2 throttle and the volts never reported over 13.48V