thanks for all the reply's!
Bartamos thanks for the wiring. I heard from the friend of ours (who is really good in these things) there should be a little light connected. I also did some research again today. From what i found on the internet:
The cable from the big stud goes to the battery.
terminal 1 goes to a little light. and from this light to the ignition switch.
Terminal 2 goes back to the big stud.
is this correct? i made a little visual so you can see what i mean.
I really appreciate your instructions

but I'm not that good with electrical wiring so i really need a visual otherwise I still won't understand
