@HS30-H I found and used this wire for my electric fan controller. The harness had the "blue tape" (visible in the picture) which seems to be the Datsun factory method of identifying wires for some optional use. The wire is 12v switched power when the ignition is in run and had a female bullet connector. Do you know what the Datsun intended use for this was?

Here's a link to our wiring diagram collection..  probably need to look that one up.

https://www.classiczcars.com/files/category/1-wiring-diagrams/

Year is almost always critical in asking questions about wiring.

17 hours ago, SteveJ said:

Year is almost always critical in asking questions about wiring.

As in my sig the car is a 1971, built 12/70 HLS30-17486

43 minutes ago, w3wilkes said:

As in my sig the car is a 1971, built 12/70 HLS30-17486

I don't like to assume.

I can faintly see what looks to be a green wire in your photo that has a female connector. Green comes off the ignition fuse. 

If your car started life as an AT car, I would think there could be a green wire for the kickdown switch in that area of the engine bay.

Thanks for finding that in the wiring diagram! Car has always been a manual tranny. Yes, the wire is green. I guess it was a good thing that my car is a MT so that wire was available for me to repurpose! With that wire being in the engine bay I guess the relay to the K.D. solenoid (if present) would be in the engine bay?