fan controller question

26B16891-4700-4A61-B751-E3C7C7F60533

The fan I have is one removed from a car in the junkyard with the wiring that came it’s it, I am confused by the a and b in your diagram, the wires on mine are a large gauge green wire and a smaller gauge black wire I am unsure of which one needs to go to the relay, I currently have it setup to send the green wires to the relay and the blacks to chassis ground.