Shouldn't be very hard to figure out and repair. The heavier wires are probably going to the pump start relay or master valve. You can check this at the timer, they are labeled. The smaller colored wires are going to valves and the white should be common returns if it was wired correctly. Again check at the controller. I have seen systems where the colors were switched in the field. Depending on how many valves you have each zone at the controller will have one, maybe two wires attached.