W126 Radio and USB sockets

When I bought my 300SE about four years ago, it came with an early 2000s era Kenwood CD player.    At the time, I assumed I would need to replace it, as it wasn’t working.   Turned out the plug had come out of the back and it actually worked fine.   It wasn’t a bad unit, as it could play MP3 CDs, display track information and so on.     My main problem with this radio was that it would occasionally cut out, and only work again if I removed and plugged the face back in.   The W126 radio is a DIN unit, so replacement options are easy to find.

My 300SE is the closest car I have to a daily driver.   Before COVID19, I used to have it on full registration.   Since then, it is on club registration (restricted), as I am not driving every day.   Should that need arise again,  I couple move it back to fully registration.   Right now 60 days per year is fine with the other cars I have.

In replacing the system, I had a couple of requirements.   I wanted a radio with a bluetooth function for calling.   It needed to have the ability to play music from a USB stick, and I wanted to be able to charge my phone without having the ashtray open all the time.

My 560SEC has a radio that does most of these things and sounds really good.   Its an Alpine CDE147BT.   I found another one of these on Facebook marketplace for $50.   It was missing the surround and the DIN frame, but came with the microphone and wiring harness.    It had been removed from a BMW E30 that was sold.

A couple of years ago I also purchased the bits I needed to create a USB power plug.   At the time, I was going to mount it behind the dashboard of my Traction Avant.    I never got around to fitting this before I sold the car.    The first component is a transformer to convert 12v from the car’s electrical system to 5V for the USB plugs.     The second was some plugs that could mount to the dashboard.

W126 radio

I leveraged the power for the cigarette lighter for my USB power ports.   Once I had the USB port there would no longer be any need for the cigarette lighter.   Doing it this way also allowed me to leave the factory wiring intact.   The power draw should be the same as an accessory plugged into the lighter.

From there, I cut a small hole in the coin tray to mount the USB ports.   This is the only non-reversible modification I did to the car.   My coin tray isn’t in great shape as the MB-Tex is cracked at the bottom.   At some point I will find a good used unit in better shape.

W126 radio

W126 radio

I used a dremel tool to cut the hole in the plastic housing.   The USB ports then went through that hole, with the top one going to my power source and the bottom one to the W126 radio input.    I could add another power port later as my voltage converter has two outputs I am only using one.     I used some cable ties to make sure the plugs did not come out as the power one was a little loose.

Installing the radio was straightforward and I did not take any photos.   It was just a process of crimping the various wires to the wiring harness for the Alpine.   I re-used the DIN mounting frame and the bezel for the Kenwood which was not a perfect fit, but better than nothing.

W126 radio

The final step was mounting the microphone on the side of the centre console. While I was at it, I also removed a rats nest of old wiring for a previous car kit that looked like 80s or 90s vintage.


Overall I am really happy with this modification. At some point I will change out the speakers too, but so far it sounds great. I can power my phone without leaving the ash tray open all the time, and easily update the music from the USB stick.   If my car still had the original Becker, I might not have done it.   But as it didn’t swapping out the W126 radio made a lot of sense.  I think the Alpine is subtle enough in the dash to look good in the car.

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