I got the radio back last year, and finally found time to re-install it.    I had also seen on Instagram where anther W123 owner had installed a USB charge port meant for an E36 BMW in place of the factory fader.    My factory fader is still working, but my 240D has two switch blanks on the top console, which is the perfect spot for a charge port.   The USB charge port was quite expensive, but it looked like a really good solution so I ordered one.

To power the Becker 596, I also planned to install another Tranzit BLU Bluetooth Box.   This is the same solution I have used in my 560SEC, 300TE and 450SLC.   I’m very happy with it.   The Tranzit BLU is a small box, about the size of a deck of playing cards that provides a FM signal directly on the antenna wire.   This makes it far less susceptible to interference.  It also provides a handsfree option for calls.

Normally the Tranzit BLU is controlled by a hidden button.  However, I had the idea of using a factory sunroof switch in the other blank switch location instead.   I didn’t have a W123 sunroof switch in my box of parts, but I had one for a W116 or W107, which is good enough to test with.

The installation was pretty simple.  I use the connector for the cigarette lighter to power the USB charge port.   The spade connectors that came with the charge port were too narrow, and not quite long enough so I made some extensions.   In testing the USB charge port, I was also able to easily pull off one of its connectors, so I crimped on a new one.

Since the USB charge port is designed to be added to an E36 BMW, it has been designed to piggy back off another accessory.   Therefore, it already had power and ground connectors for the Tranzit BLU.   I used a relay to trigger the Tranzit BLU from the Becker Antenna trigger.   That relay then powers the Tranzit BLU and also triggers the power antenna.

Instead of the button that comes with the Tranzit BLU, I wired in the sunroof switch.  I used a multimeter to work out which of the four pins are activated when the switch is pressed forward.   Essentially the way the switch works, is when it is pressed, it joins power to one side of the motor, and ground to the other side.   Thus, pressing the switch the other way reverses these connections, allowing the motor to run in reverse.   I assumed for this purpose I just needed to make the connection to trigger the Tranzit BLU.  Turns out I was wrong.

I wired it all up and did a quick test of the system.   I was able to pair my phone and play music through the Becker 596.  However, the switch did not work.   I tried a few more pin options to no avail.   I had assumed that the switch was ‘dumb’ and just made a connection to trigger a press of the button.  However, it was looking like that was not the case.   I got the Tranzit BLU switch and connected that to a multimeter.   On very high resistance settings, I was able to trigger a change in resistance when pressing the button, but it wasn’t constant.    Given there appeared to be more to this button than I anticipated, I gave up and put the switch blank back in place.    The Tranzit BLU button is now on the steering column out of sight like in my other cars.

Despite the failure of using the sunroof switch to power the Tranzit BLU, I am very happy with the setup.   The correct Becker is back where it should be and I can play music through my phone and make and receive phone calls.    I am taking the 240D on its first road trip this weekend, so having music will be great.   The install is totally reversible with no factory wires cut.

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The Europa 596 was the lower end radio supplied by Mercedes Australia.  It was the main radio supplied in most W123 models from 1979 to mid 1981.   It has mechanical radio presets, a cassette player and AM/FM function.   The Europa 596 does not have the ‘wunderbar’ auto seek function or the auto-reverse feature as found on the Becker Mexico cassette 374 that was installed in my 1979 Mercedes 280SE.

These radios have a black plastic face with the ‘washing machine’ style knobs.   Personally I don’t think they are nearly as elegant as the pinstripe radios.   They do it in well in a base model like a 240D that has the black plastic console.

In order to test the radio properly, and send it off to be repaired, I decided to remove it from the car.

Removal of these radios is similar to other Becker analogue radios.   The knobs pull off, allowing the face to be removed.   Unlike on the pinstripe radios, the surround stays on the radio.   Hiding behind the face are the two brackets that secure the radio to the car.

The 240D is very original in that it still has the original radio, and the factory fader is still in place.   However, when I removed the radio, I noticed something rather odd.   Screwed to the back of the radio was a relay controlling the antenna.   This is rather odd, as the power for the antenna is just a trigger, and the antenna gets its power from a separate harness.   In principle, there is nothing wrong with it, but I didn’t like how it was getting the power from the hazard switch.    The power to the radio and cigarette lighter would have been a far more sensible approach.

I wondered if the antenna in the boot had been wired up to take power from this setup, so I checked the antenna in the boot.   While the antenna didn’t look factory, it was wired up as I would expect with a grey trigger wire and a power wire.    Going back to the radio, the additional relay had two blue wires going through the centre console.    One was blue/grey and the other blue/brown.     Turns out the blue/brown wire was the antenna trigger.    Not sure what the other one is for.

I decided to remove the whole setup.   While the Europa 596 was out to be serviced, I installed the trusty old Europa II I had in the 250SE for a while.   The Europa II is also a once piece unit and has basically the same connections as the 596.   It certainly wouldn’t do to drive the W123 around with no Becker.    The Europa II is what was installed in US Market 300Ds in this era (the 240 getting the Europa Mono).

The Europa II looks great in the dash, and and it’s tempting to leave it there.   However, the 596 is the original radio, and I will re-install it assuming it can be fixed.

While I was playing around with the antenna trigger, I accidently blew the fuse.  When I went to change it, the fuses were badly oxidized, so I decided to change them all.   This is something I like to do with a newly acquired Benz.

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