The Euro Switch is the "standard" switch gear for the European and RT-P models that give the rider the ability to turn off the headlights. Many American riders like to install the switch for use on an auxiliary lighting system.

The BMW Part Number is # 61 31 2 306 178  (MSRP $76)

The unit replaces the entire front switchgear, including the Turn Signal Switch, Starter Button, Kill Switch, and Turn Cancel Button.

Sean Franklin  notes that "If you want to install it as intended, it's a plug & play operation - there is a shorting plug (Jumper Plug On US RT's)  on the harness in your RT that is removed, and the Euro attaches in its place. You'll have the ability to run no lights, parking lights, or full lights. Many people buy this switch but do not hook it into the intended harness directly - rather it to switch auxiliary lights instead. If this is what you want to do you will need to go through the wiring diagram."

If you intend to use the switch for other lights, Sean notes that the first thing you have to do is decide exactly what you want: " What behavior do you want from the Euro Switch? You have three positions on the switch, so you can define three "states" of lighting for your bike. I know some people have simply used it to control the driving lights, with no effect on standard lighting at all. Others set it so that one position has all lights off, the second turns on only "Standard" lights (headlight, etc.) and the third has "standard" plus auxiliary lights."

If you decide that you want it to affect any of the stock lighting, that will complicate the wiring a bit, but the Haynes book gives you the information you need to determine where to cut & splice. Also, as I recall the "off" position is an Open position, which means that any lights controlled by the Euro will be completely off when it is set there. Any lights you decide to leave uncontrolled will still be on."

I think what most people do is the following: 

• Position 1 - All lights off (Useful in case of low battery or bad charging system)
• Position 2 - Standard operation (Headlight + tail light ignition switched)
• Position 3 - Standard operation, plus driving (Auxiliary) lights on

Refer to the Haynes Manual for a better idea, but basically, The Euro-Switch wiring colors are as follows:

• green & blue: Ignition switched power to the Euro switch 
• gray & blue: Power from Euro switch to parking lights (position 2) 
• white & yellow: Power from Euro switch to headlight (position 3)

Basically, you want to combine the functions of position 2 and position 3 into position 2. Simply put "take the headlight and parking light leads and solder them together on the pin normally for parking parking lights only" 

To set up the switch for use with Auxiliary lights as noted above:

1. Cut white & yellow wire above the connector about an inch above the connector; 
2. Connect the short white & yellow stub to the  gray & blue wire at connector; 
3. Connect white & yellow end from Euro switch to Auxiliary light relay coil.

As noted above by Sean: US bikes may have a set of jumper wires at the connector instead of the green & blue, gray & blue, and white & yellow wires so that lights are always "on".