Just so you know, a truck that is wired for gauges in the cluster does not use the I terminal. They did use the I terminal on trucks with the idiot lights, and off and on through the years depending on how the truck was optioned. Instead of using the I terminal to trigger the alternator to come online, they hooked the ignition power wire to the "s" terminal of the regulator. Ford had two different ways of wiring the old separate regulator charging systems.

 

You are correct, I only mentioned the test for a 4 wire connection since the post mentioned an idiot light. I don't think anyone makes a point style regulator anymore. Even some of the ones with a tall cap have electronic guts unless you find old stock.

 

I already forgot about him mentioning the idiot light. I figured you probably already knew what the score was though. Just covering all the bases in case someone down the road finds this thread.

 

First off, welcome to FTE John! And a very nice truck!
Is that a re-paint, or just a really well preserved original? Not sure if it's a factory color, but it looks like it certainly could be.

I know you got it working already, but figured I'd just clarify something here. If you're seeing less than about 12.5v in the system, the alternator is effectively not charging at all.
Just to keep the battery at a charged state, you probably want to see something above 13v at a minimum. Anything less and you're going to be running (or not) on a dead battery soon enough. Usually you expect to see 14v to 14.5v while the engine is running.
Maybe you knew that already from the previous discussion, but the way you worded it I thought it'd be good to mention it for future reference.

One thing I always recommend on older vehicles that still have glass fuses, is to remove all the fuses, clean the contacts (and the fuses themselves of course) and then re-install them.
This act breaks up any minimal resistance that has built up over time. If they look clean, great. But even if they look clean they can build up this surface resistance that impedes flow. So it's a good quick, easy and cheap bit of maintenance. Once it's been done, you likely don't need to do it again for a few years. But that first time can really wake stuff up if it's never been done before.

Bearings are always what got my alternators. Never had one stop charging to this day. But I probably replace them too early too, as I've got this '93 that has a rattly alternator that I'm not interested in replacing yet, and it'll probably keep working for as long as I own it.
More likely I'll change it anyway just to get rid of the annoying noise!
Most better stocked auto stores will even have the right bearings in stock for a few bucks and you can do it yourself. But I'm running out of extra time for the fun stuff, and end up buying someone else's crap first.
More on that "crap" thing later...

And I'm curious about your setup now that the others have brought up the whole 3-wire vs 4-wire regulators. Which one is yours?
I thought that after '80 the trucks that had ammeters still had a battery light. Is that the case with yours? Or do you only have the light?
I sold my '83 so don't have a point of reference and didn't bother to look up the images available around here.

As you probably realized, the light remained on because the alternator was not charging sufficiently and it was just doing it's job and letting you know.

Just FYI, don't leave the wires connected for long. If you happen to leave them connected and walk away to do other things, you will certainly drain the battery fairly quickly.

As you will read in the forums, the situation with new parts these days is dreadful and dire. Some items seem to have such a high failure rate that there seems to be more bad ones than good ones sometimes! The starter relay/solenoid for one, but voltage regulators and ignition switches and a few others as well.
It's so bad that sometimes going to the junkyard to find an old original part is more desirable. Yep, it's that bad...

Anyway, good luck with your great truck! Hope that the "wiring expert" PO didn't mess with it too badly. You could have a good reliable and fun truck on your hands.

Have fun.

Paul