So many cables were needed for this setup. There are four buttons on the dashboard to control the lights. Each button requires 4 wires, 2 for the internal LED and 2 for the button connection. I soldered wires long enough to get to the electronics board in the back and labeled each one with the button and its purpose. I also put a switch on the back hatch for the water pump. This is an emergency button with a cover. I did this one so it does'n't accidentally get turned on and two so I could hit it off quickly. This specific button is rated for 12v and 10amps because it directly drove the water pump from the battery. There are also four wires two to each of the headlights.

All of the wires in the front went through a 1/2 in hole in the pressboard at the back of the cab. It was 1/2 an inch above the floor on the drivers side. I did this to keep them all together and then covered the cables with cardboard and duct tape so my son wouldn't trip or play with the wires.

The wires for the buttons in the front were taken from an old computer I scrapped. Only 5v low amps was transmitted over them so they were perfect. The buttons were purchased for the train last year and reused. The water switch was purchase at RadioShack on store closing sale for $0.70 and the light, water pump cables were all 12v car cables (not sure what gauge they came with the trailer lights). Know the volts and amps going over the cables so they can adequately handle the load.

SUGGESTION/WARNING:

Just be careful when you're playing with wires and do tests all along the way. I almost caused a problem (and burned myself but not fire) when I mixed the Power and ACC cables on the water pump switch. The cables got hot enough to do a light burn of my fingers, but nothing too bad and it was easily fixed.