Ok?

Since you just drove the car for 15 miles the system voltage and a good battery should have stabilized at less than 14 volts. We are talking tenths here, so I hope you are using a digital meter.
The car is cranking over like it's got a good battery in it, I assume?

If you had lights on or other current draws the voltage should be down a bit lower. A .5 lower or like 13.2 being the lowest while idling.

If the regulator is seeing more of a voltage drop of the system it will want to and should try to kick it up higher. Trick is, its dependent upon the engine revs! Idle usually gives you a lower reading, just because!
If you rev the engine it should vary a few tenths but all below that 14.2 volt high tide line.

A heavy steady 14 volt reading is not what I call normal. It should be fluctuating under system loading or alternator speeds.

The regulator is either malfunctioning or is not getting a good reading of the entire system, i.e. Connections.


You did not actually say you got 0.000 on the ground side to the alternator housing, engine block and body of the car with all this back to the negative battery post. This can make it not a ground issue but a internal regulator suppling issue.

You should also get the same 0.000 reading on the B+ (Big Red Wire) back to the positive post.
This helps rule out bad wiring back to the battery via the starter connection way down there below.

Pulling that alternator and giving it a good eyeball all inside where the regulator goes, has to be done IMHO.
There is the questionable regulator housing, contacts and brush lengths. Deep grooved or overheated (bluish tinted) slip rings can cause intermittents.


Since one of the grounds, from the exciter wiring, is from the instrument clusters bank of diode light circuitry, you have keep it in play. The repeated 14 volt output reading keeps the regulator in play, for me!
It uses an instrument light in its conversation to you.

The regulators internals, that are not repairable you the way, could have been damaged from brush arcings or a previous bad battery cell.
Even cable jumping another car system with a "questionable electrical condition" can damage yours!
Ever crossed the leads, even a momentary flash?

From my stand point, inspect or inject a total replacement spare alternator into this act!

These things are like toilet paper, you are bound to have to change the roll, if you drive or live long enough!

To quote General George S. Patton. "Make your plans to fit your circumstances."

I am no way a Mormon but I do store lots of toilet paper!
(:-)

Phil