Blackout on 280ZX park lights.
Caused by deterioration of the electrical contacts on the light Combination Switch on the steering column.
I cleaned the contacts and then proceeded to move the electrical load from these contacts by inserting three interposing relays. One for the park lights and one each for the left and right head lights.
Electrical circuits are in the pdfs attached.
The circuits for the 260Z are quite different and required a 12 core cable into 4 interposing relays.