There are several ways of wiring a Ranco controller, depending on which model you have and what you want it to do. I'm assuming you have a 120V supply voltage to the controller, a 120V load and a switch that is normally open/off.
I can't see clearly what's going to what in the picture. Assuming the wires coming in are using standard colors (Green = ground, Black = hot, White = neutral)
- It looks like the wire cable on the left is the male/input side and the one on the right is the output/controlled side, is this correct?
- The two green wires coming into the box are grounds and should be connected - are they both going into the wire nut?
- there's a green wire going into the upper terminal block - where does the other end go? Is it in the right (common) terminal of the lower terminal block? is the bad wire that goes up towards the upper terminal block connected to the same terminal as the green one? It looks like they used a green wire as a jumper to connect the hot wire to the common terminal in the lower block. It will work just fine but it's sloppy practice to do so.
- The two white wires should generally be connected together; I'm guessing the loose wire is supposed to be in the same terminal as the other white wire behind it.