A few tweaks and the Roadster seems to be running well and not overheating - even in Florida's early summer heat!
A few quirks still... the temperature gauge changes + or - 10 degrees depending whether the headlights are on or off!! It's almost an instantaneous change. Must be some sort of short. A little concerning when I turned the lights on while stopped in traffic... only to see the apparent engine temp jump to Hot... not that the gauges are that accurate!
Not a short but likely an extra unintended current path for the draw from headlamps which manifests as a voltage drop to the instrument circuits. As John suggests could be the troublesome PCB.
An important check would be to ensure voltage measured at headlamps is similar to that measured at battery with headlamps on, to ensure they are working as brightly as intended. If it's within say 0.5 volts then it might be easier to live with this situation rather than spending time and money sorting such an illusive fault.
