For what it’s worth…….
My instruments are Smiths/Caerbont.
My fuel gauge went zero but was intermittent which always makes it difficult.
Then my temp gauge went…intermittently and not necessarily at the same time.
I then realised when the instruments went then so did the illumination.
I could then reproduce the problem at will. Turning ignition on all would be ok including, with the lights on, instrument illumination. But, turn the ignition off and then back on and no instruments or instrument illumination. Main car lights were not affected. Leave for ten minutes and the whole process could be repeated.
I checked the wiring diagram ad nauseam, every earth, every connector, everything.
I bought an MFU that Rog referred to and all is now ok.
Cost aside, fitting is a doddle compared to my initial thoughts of the problem being the petrol tank sender. My car has the “immovable “ wood section across the pump/sender unit. Ugh!
