Yes, I'm beginning to understand the term "Italian Wiring"! Looking at the wiring diagrams the window switch lights are connected directly to the headlamp switch so the rheostat is not involved and they don't dim. The rheostat feeds the binnacle lighting (which I have working although mine doesn't dim) and it delivers output for other lighting through Connector A pin 6 and Connector F. As I don't have 12V at Connector A pin 10 on the HVAC I suspect a poor connection from Connectors A or F on the binnacle. I'm going to see if I can have a look at these by lying on my back in the footwell but I suspect that's going to be difficult.