I took a look again at the area at the regulator. Nothing like that relay! Not even a cable going there, which I could follow.

I tried to look underneath the dash, but saw nothing as well. The buzzing sound seemed to come from there anyway.

Because it is very hard to see something there, I would like to remove the dashpanel there. I tried, but could only move it forward for about 2 Inches. Of course I had removed the covers of the steering column.