I had a fan switch fail recently, and when I searched for fan switch info I found information that seemed conflicting. So - here is what I have on my Skorpion:
Outer switch is the fan switch. M14x1.25 thread, 95/90C. I ordered this replacement from Amazon: http://tinyurl.com/63n7x6b
Cost was $12.27, and what I received was *exactly* the same as the original, right down to the stampings on the body. The switch appears to fit a wide variety of 80s BMW cars. Specifically, if you order a switch for a 1987 BMW 325 you should be safe as it supposedly fits all variants of 325 that year.
Inner switch is the idiot light switch. M10x1 thread, 105C. I didn't need a new one so I didn't research this one any further.
There you go; hope this helps someone in the future.
Sam