The middle wire is used for low speed input so you can basically dis-regard that wire lead. The DC Controls were a nice product-I personally did not have any problems with the few I installed at the shop for my vehicles, but I had several customers have issues with the controllers-one was user error and the others were presumed unit failure which I was contacted about and helped or tried to take care of the problems. The Spal units work in a similar manner but not identical for obvious patent reasons and they come with weatherpak connectors, nice wiring loom, etc. It works off the coolant temperature sensor which is nice but I like the cooling theory behind the DC Controls a little more. If you were to weld a bung into the lower water pump arm and thread the sensor in at that point-you have the best setup imo.