I haven't posted for a few days but have been using the multi-meter to test things like continuity (fuses to insure they really are okay- one suggestion; new and cleaned battery cable ends, new buss fuses, etc.) and such. Getting familiar with grounds and checking what I've done prior. Nothing seemed to be working. Then, the spirit of Ohms got involved - last night, showing the Airstream to friends (and Air Forums members from Georgia) who were visiting. We also gave them a tour of the trailer. It was after dinner (thus dark, needing light) and also after discussing the background related above. So we showed them through the trailer, turning on the lights and showing the difference between warm white LEDs and white-white LEDs and the replacements in the overhead and such.
"And here, in the overhead control panel," I related as I lifted the tambour door, "is where most of the problem is..." and pushed the water pump - and it cycled! The panel lights worked, so did the meters, and the jack. It's all "fixed."
Well, not so fast. Obviously, we moved "something" that caused the original ssue and maybe moved it back trying to fix it, or in turning switches. I'm still thinking its a grounding issue and will check some more. Or it may be in one of those light switches, too.
But, it is working today! (I expect to see an English "Lucas" sticker somewhere!)
I'll keep you posted... but I knew those of you who have contributed so much to my newfound electrical knowledge would want to know - and that you all would appreciate how it all just seemed to "fix itself."
Thank you - all of you - for responding, thinking it through with me, and helping me to learn more about the systems of our fine Airstream!
CHEERS to you all!
ps - if the problem resurfaces and I find the real culprit, I'll update!