Do you get 12 volts across the terminals on the big black plug? I might be tempted to supply power from elsewhere, just as a test.

 

I do not get anything across the terminals. Can I just run a temporary wire from alt+ to one and then ground to the other?

 

Actually, I think I may have done that test already. With everything wired up, if I take the non-powered wire to the regulator off and ground it, that SHOULD be feeding 12v directly to the coils, yes? I'm growing increasingly suspicious that the alt may be bad despite the test done on it.

 

You want a switched 12 volt feed to the field coils, otherwise, your battery will be dead every morning. Think I would leave the black plug out of the equation altogether, just to see if it actually does charge. Gauge in the dash won't work.....

 

Update: Everything was pointing to a bad alternator, which I was disregarding because it'd tested good when I took it in. Today I removed it AGAIN and took it to an alternator specialty shop I wasn't aware of before, who were able to diagnose an intermittent fault in the alt, possibly a bad brush or brush spring. Warranty replaced the alt and it's good to go!

 

Oh such fun. Gotta love it when new parts are bad, right out of the box.

 

It was a year and change old, so not BRAND new, but definitely too new to have gone bad. The previous owner bought lifetime warranty everything, at least.

 

And that carried over to you? That's surprising. Generally, the 'lifetime warranty' is only for the original purchaser.

 

I wasn't sure, and carefully did not mention that.

 

Good Plan.