I just bought a 1973 240Z and I'm trying to understand some of the wiring modifications made by the PO. I think I have them mostly figured out but this one baffles me. There is a red wire running from a plug near the passenger vent.

To the ballast resistor (yellow wire goes to the electric fan).

Anyone got any idea what it does?

I believe that the interior is for the accessory relay. I think maybe someone is tapping off 12VDC to go between the ballast resistor and the accessory relay. I'm guessing someone was looking for switched power, and if I was a betting man, I would suspect a bad accessory relay precipitated that hack.

I believe that the interior is for the accessory relay. I think maybe someone is tapping off 12VDC to go between the ballast resistor and the accessory relay. I'm guessing someone was looking for switched power, and if I was a betting man, I would suspect a bad accessory relay precipitated that hack.

Any idea what that relay does? The car is in a million little bits right now so I can't just unplug it and see what stops working.