Hi there!

I have to say this, for me, it seems like you are looking for rabbit in too many holes!

First of all the charging voltage of 13.8 is normal or even less depending on the charge of the battery and the temperature of the system in general.

The 14.2 reference is on the top end past that you would be over charging the battery especially on long trips.

If you had a dash mounted voltmeter you "could see" that the meter will swing up that high just after starting the engine, on a full or normally charged battery but After a bit, it will drop back. A voltage as low as 13.2 is still ok. The regulators job is to maintain approximately 1.0-1.5 voltage above the battery or systems draw down of current loading.

You said you checked for voltage drop across the battery but I don't understand what you expected to see in relation to what?

If you were using the voltmeter for ground checking you would not put the meter across the post but rather parallel to the systems cables and ground points. Anything but zero's to 0.02 means a bad ground.

As far as the alternator, it is rubber mounted and has to have a separate ground wire from its housing to the engine.
You might want to make up a new wire for it as they are troublesome!

You can do a quick check with the voltmeter by running the lead from the alternators aluminum housing and back to the negative post to see if you get only a set of zero's. You can do this while it running as well. Trick is, it just might be fine at the moment and later flake out!

As far as the exciter wire being on or off and it charging the exciter wire is only needed to "tickle" the alternator during it first rotations to start an output. Above certain RPM's it becomes self excited.

It's only when you have absolutely no current output does that the battery idiot light come on! It sucks for giving you a forewarning of the condition of your alternator and battery system.

The trick with the instrument lights appears that it's circuitry is looking and finding a alternative ground route, though what, I don't know. It's not the first time Brickers have had this problem.

All I can say it might be an alternators grounding problem as it seems related to that sometimes.

I might add as well, that people talk about the bulb failure sensor but that's a whole other issue.
I can't help you with it as I have not experienced any problems of that sort.

Keep searching FAQS for instrument cluster issue as a fall back. You have been into that thing so it could be a loose ground or a wire from the plugs to the cars body? That's Just a guess!

Phil