Do It Yourself

Installing an Auxiliary Audio Input
by Matt Crawford, Desert Stars Section

With the newest Mercedes-Benz models, owners can have almost any audio source they wish, from old-fashioned AM radio to satellite, MP3, and smartphone. But for those of us who have models that are more than a few years old, our choices are limited to radio and CDs. Or are they?
Editor’s note: When I received this tech tip from Matt Crawford on how to install an auxiliary input cable in the W203 and W209 cars – the C-Class and CLK coupes built between 2002 and 2007 – it was the answer your editor was looking for to get his 2005 C55 into the modern age, tunes-wise. It turns out to be simple enough to do yourself and will cost less than $50.  
The key piece of information is that you can order from your dealer a cable harness (part no. A210 440 50 05) that connects to an existing open harness plug under the floor covering in the passenger doorsill/footwell (1) and can be installed into a factory hole inside the glovebox. This cable harness may also work on the W210s, but I didn’t check.
I purchased the auxiliary input cable from my dealership in Miami for just under $50. The dealer didn’t have it in stock, but was able to order it for me within a few days. I installed it using only a small flathead screwdriver and a hex drive, working in my condominum carport.
The first step is to remove the panel on the right of the glove box. There are clips on the rearward end of the panel. The forward side (the end nearest the engine), along the door seal has tabs on it. You pull out on the rearward side to pop those clips, and then pull the whole piece about an inch rearward to slide out the tabs in the forward section.
Second, remove the plastic trim on the doorsill (1). This pulls straight up. It clicks and pops, but should be a straightforward pop-out.
Third, remove the right kick-panel in the passenger footwell. This panel has a small hex-head screw right in the middle of it holding it in, with a cover concealing the screw. I used a small flat-head screw driver to remove that cover, then removed the screw with a hex-drive. There are also two metal clips holding this panel onto the car at the door sill area. Pull back the rubber by lifting it off the car at the curve from the sill. You have to remove those clips; from what I can tell any other way will break the plastic of the panel. The clips are attached to the panel, so I used the same screwdriver to pop them off the car, and the panel with them.
Fourth, open up the wiring harness casing in the door sill (2). You will see the white plastic harness plug into which the aux cable will plug (3). It may take a little digging with your fingers to pull it up. Plug the cable into the harness (4), and then run it up the side kick-panel area to the glove box side.
If you want a clean install, you can break off the round panel blank on the wall of the glovebox where the cable plug will go. Using my flathead screwdriver, I broke the four tabs that held the blank in place and snapped in the cable plug. Or, do what the editor did, and simply run the cable under the footwell panels to come out near the console.
Then, put everything back, and plug in your input device with a double male plug connecting the earphone output on your iPod or whatever into the aux plug. Holding down the CDC button on your audio controls will activate the aux input and connect your device directly to the audio system. No, this will not allow any iPod controls or power but it is an inexpensive way to have the option of another sound source. I actually use mine for a satellite radio and have attached the small XM radio under my cup holder. The editor connects his old iPod to a power converter to recharge it while he’s using it, and the longer cable allows the driver or passenger to select the tunes on the iPod’s control panel (top picture).