I actually will buy one eventually. I have to fix or replace the Wagoneer's lighter first. On the Barracuda, the lighter is in the ashtray and not a location where its very useful.
For diagnostics, this works pretty well.
View attachment 1715314950
So as best I can tell, since I didnt drive it anywhere, the 15 Volt regualtion was temperature related as today it was down to 14.7 to 14.8 at startup.
The analog meter was checking voltage at the temperature sender connection - sender disconnected. Might be resistance in the circuit since the fuel gage is roughly correct (for a repop).