headlight switch

A long time ago (in a land far away...) So back in 2005 my headlight went out on a trip which made me have to stop for a motel on my way home. I replaced the headlight and still no go. Found out it was the switch so I got a used one off ebay. I also installed relays for both the high and low...

I've had several bouts of this problem over the last two seasons. When it rains or I take the bike to a carwash the horn will blow on its own. Sometimes a quick flick will stop it but other times it just keeps blowing until I shut the bike off. For the last week it wouldn't work at all but today...

On my 1983 R100, I have a headlight switch on the left handle bar (it came to me that way). I was told that this is a European switch and that the PO probably fitted it to the bike. I am in the middle of my swap the Vetter Windjammer III for an RT fairing and am trying to find a wiring spec...