Charging issues

[carrera73rs]

Pelicans

I have an 81 911 SC which at sometime before my acquiring of the vehicle had the external voltage regulator switched to the 82 and newer version internal regultor on the alternator.
About a year ago my battery became so low it would not start the car. I charged the battery and it started easily.
I checked the voltage at the battery while it was running at above 2000 rpm and it was at or about 12.3.
The alternator was removed and taken for testing where it was diagnosed as good.
I installed a digital voltage gauge in the cigarette lighter to more easily see the charge levels.
When the car started from cold it would charge at 14.3, but after a while, 15 min or so would drop to 12.3.
The internal voltage regulator was swapped out with a new Porsche part and it ran as it should, 14.3 after start up and around 13.8 with load on.
After a few weeks it quit charging again, showing less than 12 on gauge and at battery with volt meter.
Alternator light has not come on while running but it does light up either when ignition is turned on or shut off so bulb does work. I am unable to check which at this moment as I am away from car currently.
Is this new voltage regulator defective or is it the alternator, or am I looking st something else.
Thanks for any help you can lend.

Kirk

[DRACO A5OG]

Pull the battery and take it to a FLAPS and have it tested. or better yet if you have AAA call them out and they can diagnose the entire charging system.

Couple of things:

1 Battery could be compromised
2 The Connectors could be split from over torqueing ( My issue ) and not allowing the alternator to do it's job. Your voltmeter confirmed alternator is working but battery is showing a failure.

Minimum voltage we need is 12.5+ after an hour of charging or driving.