Hello, I have a 2000 e320 4MATIC Wagon. I wanted to run a cooler in the trunk (boot); however, it looks like the 12V socket I have in the back isn't hooked up. I do have the socket there, but when I open up the spare wheel compartment, I see no wires running into the 12V socket. I find it strange that the socket is there, but the wires aren't ... can anyone help? Am I missing something here?