I recently retrofitted a full NTG 2.5 entertainment system to my W219 CLS (see this post).

Among other things, this system has the ability to receive DAB radio broadcast here in the UK by using an additional DAB Tuner module. I managed to source the genuine Mercedes part (A204 870 54 90) and fitted this into the car. This guide outlines the steps I took to get this working.

Connections

Like most equipment in the system, the DAB Tuner needs:

a) A connection (IN and OUT) to the fibre optic loop (MOST bus)
b) Normal wire connections for the Power, Ground and Wake Up signal

and also (obviously) requires an antenna connection to receive a signal in the correct band/frequency for DAB.

Antenna Connections

In most modern cars, the antenna is often incorporated into the rear windscreen or in a small stubby roof ‘shark fin’ unit. In more complex systems, the signal is then fed into an antenna amplifier that boosts and splits the signal into the different frequency bands for various applications (e.g. FM Radio, GPS, DAB, DVB-T/TV etc).

The disadvantage is that if the car only has the output for FM Radio, that antenna feed cannot be split after coming out of the amplifier as the DAB frequencies are filtered out in the amplification process – which makes getting a signal for DAB a little more difficult.

In this case, there are a couple of options:

a) Get a new antenna amplifier and loom from Mercedes that includes the correct outputs for DAB

b) Use an external (or internal) DAB antenna. This will be entirely separate to the main antenna system in the car and depending on the quality of the antenna and where/how it is mounted, may not give a good signal.

Since my age of W219 (i.e. pre 2009) never came with DAB as an option, I could have gone with the expensive route of replacing the antenna amplifier and loom, but since the car did originally come with a digital DVB-T Tuner (when the car had NTG1 – since removed), I had a third option:

c) Use the now dormant 4 connector DVB-T antenna feed. Since the DVB-T UHF frequencies are very similar to DAB, this should work.

The 4 way connector must be partially dismantled and the YELLOW ended cable in the 4 way block removed and plugged straight in to the OUTER of the two Fakra inputs on the DAB Tuner. The inner one is unused as it is for L-band which is not used in the UK and the remaining 3 connectors on the TV Tuner antenna feed are also unused.

Power and MOST Connections

Since the TV Tuner was no longer in the car, I used the also now dormant power connector block and re-wired the necessary cables to a new connector for the DAB Tuner.

This required part numbers:
A002 545 84 40
A000 545 84 30

Which I picked up for around £2.00-3.00 at my local Mercedes dealer.

For the DAB tuner, the following pins are used in the small 4 way connector block:

Pin 1: Ground (Brown)
Pin 2: +12V Live (Red)
Pin 3: MOST Wake Up Signal (Pink)

I had some MOST optic cable loom and plug ends also left over from removing the TV Tuner so I reused these in the new connector block I purchased. NOTE: If, like me, you retrofitted NTG2.5, make sure the optical cable section being used is still in the loop and hasn’t been disconnected! You can do this with a bit of trial and error by powering on the Comand Headunit and seeing if the red light comes through to one of the ends – you need to be quick as if the optical loop is broken for longer than about 10 seconds when the system starts, it will stop transmitting and you need to power off and back on again.

Coding

If it has not already been done, the system will need to be ‘coded’ to enable the DAB feature in the Headunit. Mine was already enabled so worked straight away.

I’ve had no reception problems and much better performance than other in car DAB systems I have used, the audio is noticeably better than regular FM and there is much more choice!

Recommended upgrade!

Footnote: Using the TV Tuner power connectors, MOST and TV antenna feed for the DAB tuner means that if an NTG2.5 TV Tuner was to be added in the future, further wiring would need to be added and work with the antenna would need to be done to fit it. At the moment, I have no plans to add a TV Tuner and I never really used it when I had it before so for me, DAB was a more useful option.