The regulator checks out, and is working correctly.
Here's the problem in a nutshell --
The Arm terminal at the Regulator has to get at least 12 Volts from the Generator to make the Cutout Relay contacts (at the Batt Terminal) close. That puts the voltage to the battery and also makes the light go out.
I removed the cover from Regulator (to look at Cutout Relay), all wires still connected to regulator, and engine running 1500 RPM, I have the following:
Voltage from the regulator Arm Terminal to ground was 2.5 Volts incoming from the generator (That's not a typo -- it was 2.5 Volts). The Batt contact points were open, and light is on.
I then measured the voltage from the regulator field terminal to ground and also got 2.5 Volts (same as the arm terminal to ground volts).
So, my Generator is only putting out 2.5 Volts to the Regulator, which is why the contacts points on the regulator won't close.
I turned off the engine, and restarted it. Gunned the engine 3 or 4 times to about 4,000 RPM -- and the light went off long enough for me to take another reading at the regulator ARM terminal to ground -- 12.5 Volts and light off.
Restarted engine again -- and light is on -- and has stayed on forever since then.
The only thing left for me to measure is the voltage directly from the Arm Terminal stud on the generator to ground -- under the car, with it jacked up, and running at 1500 RPM. You know I just can't wait to do this -- don't you??
Can I ask you to take a Voltage reading for me? With your engine running at fast idle, (1500 RPM or over), and Gen light out, take a voltage reading from the regulator Arm terminal to ground. I'll bet it's at least 12 Volts.
That will answer things until I take the undercar reading.
1960 Hard Top/430
Thunderbird Registry Number 1231