Thank you.
Yes, I have speakers inside the door:
And I checked the options, I have "321" what points to a CR22 and "490" that identifies the sound package. I took a picture of the plug as well, actuelly there are two of them.
I cut off the thick wires that were connected to the speaker wires. I hope no more modifications made, so I will organize an used amplifier (HEAS?) and fingers crossed ;-)
Any remote diagnosis possible or hints? Thanks a lot so far!
Btw, does anyone know what the brown sheathed cable with the small plug that is sticking out of the top center of the door seal is used? It was not connected....but no application for that in sight as well ;-)