These wouldn't be British cars without gremlins, would they?
Having failed in finding a speedo gear for my 365 transmission, I set about this weekend removing the OEM speedo to install a Speedhut GPS unit.
Unhooked the ground wiring from the speedo, removed it. Just testing things before I put the new unit in.
All instrument lights are out, but all instruments work: temp comes up, oil pressure reading, etc.. ONE light works: the one that was in the speedo (it's dangling by its wires). They all seem to be using the same ground, and wired in line on the same power circuit, but only the lights are not working. But they are working for the one.
Wiring diagram doesn't indicate that light is on a different circuit than the other instruments, nor is it/they on different fuses.
go figure.
Not really asking for a solution, one way or another I'll figure it out...but you're welcome to take a guess.