Hi Toby,

What a coincidence, Last night I was fiddling with my light switch but mine is 940GLE. The reason was that I wanted to re-wire the fog lights to the parking lights. Currently the fog lights only work when the headlights are on and for this I need to have the ignition on. I wanted them to work if my parking lights instead which does not require ignition. From my fiddling I discovered that the red wire on the back of the switch is a live wire from the battery and is connected to the white wire (I think - could be grey) if i turn the switch to parking lights. Then there is a blue/white which is also a power source but the power is there only with the ignition on. The yellow white is the wire for headlights and high beam.

My car set up is that I could switch on the parking light without ignition on. But for headlights with parking lights, I need to switch on the ignition.

When I hot wire the blue/white nothing happened. But when I did the same to yellow/white headlights were on and I could hear the click from the relay. So yours may not be the switch.

Hope this helps.