Thanks Clive, this is very kind of you,
I am pleased to report that the brown and yellow has a break somewhere and when I replace this I get a charging light on when the ignition is switched on which goes almost out when the engine is running. The brown and yellow goes to.a yellow in the shunt box. See pictures below of the difference of light brightness . I am not much good at electrics but I assume the very faint glow means one side of the light has more voltage than the other so a small current is flowing through the bulb . I do get slightly more volts at the battery 25.2 vs 24.9 when the engine is running.
Does this mean the alternator is not working as it should as I would expect a higher voltage difference.
Thanks
James