Just got a 88 Pickup as my first car, and I am trying to wire up a tac. Usually theres a negative cable I can just hook up to but that hasnt worked so far. Looking at pictures of diagrams it looks like there should be another out cable that mine does not seem to have.

I've looked all around and it only seems to have the one green connector when pictures on the internet show three. Is there somewhere in this green connector that I could splice into to wire a tac?