[T Bird]

John & folks
I did a little testing with the Fluke 88. I disconnected the blue wire at the bulb in the oil press/temp gauge and at the votage regulator. I then measured resistance in the blue wire from the bulb connector to the voltage regulator connector. Resistance is .6 ohm. I believe that indicates normal resistance for a run of wire this length.

I cleaned the blue wire and red/black wire connectors at the bulb, as well as the bulb holder and bulb with isopropol alcohol. These connections were clean and shinny to start with, but since I had access to them, I went ahead and gave them a good cleaning anyway.

I fired up the car and the same symptoms present -- moderate glow at bulb at idle; faint glow at 2K RPM and 3K RPM.

I next took voltage readings at the bulb connectors themselves, as follows:

engine off/key on: blue wire = .99 volts; red/blk wire =12.8 volts; red light glowing brightly
1000 RPM: blue wire = 12.6 volts; red/blk wire = 13.6 volts; red light glowing moderately
2000 RPM: blue wire = 14.7 volts; red/blk wire = 14.6 volts; red light glowing dimly
3000 RPM: blue wire = 14.95 volts; red/blk wire = 14.65 volts; red light glowing dimly

These voltage readings at the blue wire bulb connector suggest to me that the blue wire is not the problem. Moreover, the D+ output of the alternator is a bit high I think, but it looks like that aspect of the alternator's performance is not the problem. Further, from the 15 volt readings I took at the battery terminals as indicated in my first post, it looks like the B+ output of the alternator, while again high, doesn't suggest a problem with the B+ side of the alternator. Stated more simply, this alternator is making DC in abundance at both D+ and B+.

I'm a bit perplexed why the red light remains on at 2000 & 3000 RPM, since voltage from the blue wire is greater than the voltage from the battery at these engine speeds. Any ideas?

I'm suspecting now that my problem may be in the voltage regulator. The B+ output of the alternator is out of spec low at idle and out of spec high at 2000 and 3000 RPM. I have no reference specs for D+, but it seems like D+ is a bit high too. Do these readings suggest that the voltage regulator has failed and is driving excessive output by feeding too much current to the alternator through DF?

Any thoughts would be welcome.