Your diode wire would be the upright part of the "T". This a 78 drawing so wire colors are wrong, but the T L and S orientation is common across the alternators.

Edited Wednesday at 09:48 PM3 days by Zed Head

1 hour ago, Zed Head said:

The Dave Irwin adapter converts one of the 71 wires to an "L" wire. Here's a schematic from the 1978 FSM. 1978 was the first year of the internally regulated alternator.

Interesting (to me), I just noticed that there is a resistor inline with the charge lamp. In the past I think I've seen discussions about what happens to charging if the lamp burns out. Apparently, nothing. Charging still happens.

In your case, when the diode opened, there was no current through the stator coil. No magnetic field was produced so no charging happened.

Love this discussion. I am learning a LOT. As a mechanical engineer, I do not look at wiring diagrams hardly ever. So this is a great review of circuits. Z cars have so much to teach!

Edited Wednesday at 08:50 PM3 days by Zedyone_kenobi

21 hours ago, Zedyone_kenobi said:

I then switched the Multimeter to Diode Tester. Red to black or black to red the Multimeter read OL.

20 hours ago, SteveJ said:

That would indicate a failed diode to me. Wouldn't you agree, @Captain Obvious ?

Yes, that would indicate a failed to me as well. It failed open circuit.

And by the way, for educational purposes... With the new digital meters, it's pretty much impossible to check diodes integrity using the resistance scale. It needs to be on the diode check setting. If you happen to have an old ANALOG meter with a needle sweep, you can often check diodes with the resistance scale. But analog meters, like the dinosaur, are either extinct, or headed that way.

So what SHOULD you have seen? Using the diode check setting, you should have seen "OL" in one direction, and some small voltage in the other direction. Something like 0.50 to 0.80 Volts.

18 hours ago, Zed Head said:

I just noticed that there is a resistor inline with the charge lamp. In the past I think I've seen discussions

The pics are dead (Cause photobucket sucks!!), but yeah:

https://www.classiczcars.com/forums/topic/51963-internally-regulated-alternator-trivia-bootstrap-current/ ?

3 hours ago, Captain Obvious said:

The pics are dead (Cause photobucket sucks!!), but yeah:

https://www.classiczcars.com/forums/topic/51963-internally-regulated-alternator-trivia-bootstrap-current/ ?

Glad it was nine years ago instead of nine months. My memory shelf life is not terrible but not fantastic either.

8 hours ago, Zed Head said:

Glad it was nine years ago instead of nine months. My memory shelf life is not terrible but not fantastic either.

Haha! I know what you mean.

But wow... Was that really NINE years ago? I've been sitting in this same spot for nine years???

time flies guys. My new alternator comes in Monday. I will try just adding the regulator cap to see if that fixes things before I swap out the alternator. I have high hopes