There is a sticky in the W203 forum on adding the Aux input cable.i have an 05 c240 and want to install an ipod adapter so i can play my ipod. any suggestions on where to start and if it's possible what do i need.
You could buy the standard adaptor cable which installs into a predrilled hole in the side of the glovebox.
I simply used an 1/8 inch plug and cable and used standard crimp connectors. then strung the wire under the carpet and up beside the console.