LED Rocker switches use a built-in LED to provide a clear indication that the switch is turned on, and are usually used for switching 12 volts DC. Single pole, single throw, or SPST, switches normally have two connections, one for the power going to the switch, and the other for the power leaving the switch to power the load when the switch is turned on. LED Rocker switches also have a third connection, which is needed to provide a ground connection for the LED.
Cut two lengths of red wire to use for the power connections on the switch, and one piece of black wire to provide the ground connection for the switch. Strip approximately 1/4 inch of insulation from the ends of each of the wires, using the utility knife or wire strippers.
Take each wire in turn, and twist the wire strands at the end of the wire together to make a solid connection. Slide a crimp terminal onto the end of each piece of wire, and then crimp in place using a crimping tool. The type of crimp terminal should match the type of connectors on the switch, so they fit together properly and provide a good connection.
Slide the crimp terminal on the end of one of the red wires over the lug on the switch labelled "Acc". Connect the other end of this wire to the power input of the device being switched.
Slide the crimp terminal at the end of the other red wire on to the switch lug labelled "Power." The other end of this wire should be connected to the positive connection of the twelve volt power source, for example a twelve volt battery.
Take the black wire, and slide the terminal over the lug on the switch labelled "Ground." The other end of this wire should be connected to the negative connection of the twelve volt power source, to provide the ground connection for the LED.
Connect the ground connection of the device being switched to the negative connection of the power source. You can now test the circuit. When the switch is turned on, the LED in the switch should light and the connected device will be powered.
If you do not wish to use crimp terminals, the red and black wires can be soldered directly to the switch lugs for a permanent connection.
Make sure your LED rocker switch works with 12 volts DC. Some illuminated switches are designed for high voltage AC supplies, and use a neon bulb rather than a LED. These switches should not be used in this application as they require an AC power supply.