I've replaced the European mirrors with the U.S. version and since then they move in
the opposite direction of the switch.
Now I got a new Switch (from the US / GMPartsonline) and the problem still exists.
Tomatosoup posted two schematics for me
http://www.kappaperformance.com/forum/index.php/topic,7532.msg188035.html#msg188035.
These schematics are for the 2007 / 2008 Sky, does someone have schematics for the 2009/2010?