PIAA headlights on BMW R1100GS with Relay and European headlight switch.

In this description, wire runs are marked by map coordinates for beginning and end of each added wire, along with the component the wire is connected to. Refer to the wiring diagram.

From E7 PIAA relay other switch connection, the au lights wire goes to the PIAA headlights at A5. (Represented by yellow. The PIAA wire is white with some other color.) This supplies the lights with battery power.

A5 PIAA lights ground wires go to ground at any convenient place (C4). (Represented by brown. The PIAA wire is black and some other color.) I used a bracket for some brake lines. This supplies the lights with ground.

From D7 LH handlebar switch junction box wire #1 (white), add a wire to the PIAA relay coil at F7. This supplies the relay coil with +12V when the brights are on. (Represented by tight white/black checkers.)

Prepare the European right hand handlebar switch. Cut the #3 (green-blue), #7 (grey-blue), and #4 (White-yellow) wires a couple of inches from the junction box. Solder the short ends together. This gives the headlights and running lights power all the time and simulates what the US right hand handlebar switch wiring harness does.

Cleverly slice off a section of insulation form the #8 (brown) wire. Solder the #3 (green-blue) wire to the #8 (brown) wire. This enables the #7 and #4 wires to be switched to ground by the Euro headlight switch.

From E7 PIAA relay coil, run a wire to the 4 (white-yellow) wire on the RH handlebar switch junction box. (Represented by red/white checkers.) This enables the relay coil to be grounded when the Euro switch is in the Headlights position.

At A7 Battery Positive (+) terminal, connect the thick white cable that leads to the PIAA relay switch connection at F7. (Represented by tight white/black checkers. The PIAA wire is white with really thick insulation) This lets the relay switch the lights on.

How it Works

When the left-hand lights switch is in the high-beam position and the right-hand lights switch is in the Lights position, the relay is supplied with power and ground. It then supplies the auxiliary headlights with power.

When you switch to low-beams with the left-hand switch, or when you switch to Running-Lights or off with the right-hand switch, the auxiliary lights go off.

Adding Fog Lights

Fog lights can be added with a similar circuit. The only difference is that the ground end of the relay coil is connected to the #7 (grey-blue) wire of the RH handlebar switch junction box.

How it Works

When the left-hand lights switch is in the low-beam position and the right-hand lights switch is in the Running-Lights or Lights position, the relay is supplied with power and ground. It then supplies the fog lights with power.

When you switch to high-beams with the left-hand switch, or when you switch to off with the right-hand switch, the fog lights go off.