Thanks Mex. If I get ambitious enough I will try that.
Meanwhile, since it has run the truck ok since new in late 2002, I expect it will keep doing so. That dim light must be from some leakage so it just adds to the other parasite draws when the truck is parked.
I have a solution to the TC battery charging problem where the truck engine and the inverter act as an "inverter-generator" to run the Vector 35 amper smart charger. That does constant 33 amps in the bulk stage, so I think that will do more AH in an hour than alternator charging where the amps taper, even if it started out at higher than 33 amps with the alternator improved and fatter wires.
The installation "issues" of the inverter, charger, and cables from truck back to camper have all been solved, so I will go with that method. Turned out I was lucky in the way the TC is laid out inside.
That also gets some more use from this extra gear I have lying around that were "spares" for the 5er left over after various upgrades to that.