If I'm seeing your diagram correctly, you have a braided ground wire, a co-axial antenna wire, and the 6-pin connector. What the red wire leading from the ground is/was is un-known as Mercedes uses brown for ground (as is SOP for European autos), it was added.

The six-wire connector runs the antenna up and down. If it is not working, there are a couple of failure modes, mostly involving water getting into the assembly and doing damage, some of it is reversable and I keep a couple of parts antennas around for such repairs.

Your best bet IMO if all wires are there that I mentioned, is to pull the antenna and disassemble.

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Gone to the dark side

- Jeff