If you only have 12vdc at the alt stud then the alt isn't putting out enough juice. You had it tested and verified ok so it sounds like your field's varying (through the vr) connection to ground is possibly open. Sounds like you have gone over the grounds. You replaced the vr so it would be an unlikely candidate. You unwrapped the wiring which may have caused an open cct. in the field wiring.
Here is a bit of a write-up posted by 72RTChallenger that should be able to pinpoint the problem - give it a shot. It tells you how to full field the alt for max o/p.
Check voltage, both with engine OFF and running at fast idle, AT the alternator large nut connector. Voltage should be same as battery, and at fast idle, should be "up" from the battery voltage. With the car running on fast idle, measure with NEGATIVE meter probe on the POSITIVE battery post, and POSITIVE meter probe on the alternator nut connection. There should be very little reading, may 1/2 volt, if charging hard, maybe as much as 1 volt. ANY reading upwards shows problems with the large wire going from the alternator, through the firewall, to the ammeter, back through the firewall, and to the battery. SUSPECT either the firewall connector or the ammeter itself. These commonly melted the plastic around the meter in the dash unit, causing the connections to loosen.
Also, (at least on B bodies) somewhere up near the ignition switch wiring, there is a taped up "in harness" Y splice. I've found two cars in my lifetime with these broken.
Now, say, the first test is "OK" that is, you have battery at the large connector.
Now you want to try and "full field" the alternator. Disconnect the regulator connector (at the regulator) Pull both small wires off the alternator. Take your meter (to ground) WITH THE IGNITION in "run" find which wire has +12. I've forgotten the color. Take the wire which is "hot" and hook back up to the alternator. It does not matter which one goes where at the alternator.
Now, take a clip lead (test lead) and clip to the remaining "spade" (field connector) on the alternator. Ground the other end. You should see a small spark, if not in bright sun. Start the car, and the alternator should charge "full current." Don't do this for long, the voltage will really climb if you wind up the engine. You should hear the alternator grunt and whine, if the ammeter is working it should charge. TO BE SURE, measure both the voltage (to ground) at the battery and at the alternator "nut" connection. They should be close to the same voltage, not more than 1/2-1 volt AT THE VERY MOST apart.
on the regulator check the connector for continuity. One field wire should go directly to the "right hand" connector on the regulator, and the "left" or "center" pin should go to the other, and be "hot" with the key on.
Also, as with above, hook the alternator up "normal" and try grounding the field at the regulator, which will verify that
The alternator field is getting +12 through one lead, and the wires are both good up to the regulator. Make sure you ground the correct wire, Ground the one which does NOT go to +12
If this doesn't work, but DID work when you "full fielded" the alternator, you have a wiring problem from the alternator to the regulator, or from the regulator to the +12 connection
CHECK that the regulator is GROUNDED. Scrape away the paint, and use "non rusty" bolts preferably with toothed (star) lock washers.
A few things:
If you have large wires going to the ammeter, you have the old "full current" ammeter. I can't stress enough to check, check, and recheck the firewall connector. ALL CHARGING CURRENT, ALL OF IT goes through that firewall connector TWICE.
If you have the old style ammeter, check the dash unit CAREFULLY. The slightest looseness of the wire connections shows that the plastic has melted near them and allowed things to get loose. At least some of these ammeters were held together by the very nuts that connected the wires. That meas that if the plastic softened, the wireing connection would loosen.
If you have the newer "shunt" type ammeter, they work more like a voltmeter. They "tap" a sensitive meter movement with fine wires across a section of the car wireing itself, and "measure" the "voltage drop" across that length of wire.
this is a quick diagram that is helpful
http://www.fortunecity.com/silverstone/chrysler/45/charge.htm
