Hi Denis
I can’t quite see a loose end from the picture.
But it looks like the third brush lead which connects the brush to one end of a field coil.
Hope this is of some help
Regards
Tim
Ps from the fault described this would fit
After another look if it’s the brown wire which is homeless then it’s either a main brush to earth .
Or the other main brunch to Dynamo output
I can’t quite see a loose end from the picture.
But it looks like the third brush lead which connects the brush to one end of a field coil.
Hope this is of some help
Regards
Tim
Ps from the fault described this would fit
After another look if it’s the brown wire which is homeless then it’s either a main brush to earth .
Or the other main brunch to Dynamo output