Was stuck in Norfolk on hols when had a sudden failure of the circuit that provides the taillights, front side lights and dashlight (just the backlight, not indicator lights). Main front light OK. RAC man and I looked hard for fault but no joy.... all fuses intact.... so wondered if the switch. Got home using trailer board powered from elsewhere as dark.\
Now home, have had another look. three wires from switch.... black, red and green. 12V supply to red and green when switch off and black seems to be earth or common lead. Put sidelights on and green goes to 0V and when mainbeam on red goes to 0V...... seems a strange way round by the way.
So I am assuming its a relay because if switch was faulty I would not get green going to 0V. Taken relay covers off and do not know which is which. Looked at wiring diagram and


Help and thanks
Clive