Adding Lights and Horn
How to add a light and/or horn to your internal hub kit (Magic Pie 3, 4, 5)
On the wiring harness for the throttle, brakes, etc. there is an unterminated cable (a wire without a proper plug/connector). You need to cut off some of the insulation to reveal four wires: red, black, yellow, and blue. These wires are for lights and a horn.
You can use the red (+) and black (-) wires to power lights. These lights may be turned on or off using the button/switch on your throttle.
You can use the yellow (+) and blue (-) wires to power the horn. The horn is controlled using one of the two control buttons that come with the hub motor kit.
Although the wire harness looks different, this diagram can be used to hook up lights and a horn on the Magic Pie 3 or later, it will work the same on any of the newer internal controller kits. This diagram shows how to hook up a combined light and horn, however, the red, black, yellow, and blue wires can be used to hook up a separate light and horn as well.