I'll try to see what voltage I get when reving upto 5000rpm this weekend. Maybe I should try to find a powersource at the front of the bike and try to connect my nuvi hard wire powercable (when the new one arrives). The horn is easy. When I just turn the ignition key to "ON" then it horns normaly. That one indicates me that there could be an electrical problem or the horn hates wind when driving and doesn't like to work then..... eeeuhhh
Checking the voltage (now that I know the numbers to look for) will be done.