Been lingering here for a while figured Id post a DIY as its not really a secret and can be done by anyone
I will start of saying: I am not responsible for any damage
I can assist with any questions if you get stuck along the way
I have done this countless times over the last 5-6 years I know this procedure works
There is misconception that a w204 prefacelift car needs to have the steering column changed to retrofit a newer style wheel. while yes this can be done its not needed.
with that said lets start with the w204 PFL

w204 pfl:
For this swap it is important that you purchase a wheel with these style buttons otherwise the swap wont work.

1: remove the center airbag plate and set aside
2: remove the trim with the buttons and set aside
3: remove black box and disconnect all wires going to the top
4: remove your oem airbag (your steering wheel control module is located on the airbag) you will need to remove the backing plate to access the board

5: take a look at the wires going to your oem buttons, there will be a connector with 6 wires on both sides. the w205 wheel also has a connector but it is different (however it too has a plug with 6 connection locations)
you will need to transfer the connections from your oem button harness to the new steering wheel connections.
depin the w205 buttons leaving just the plug. one by one depin your oem harness following each connection 1-6 and install in the w205 plug. do this for both sides



your setup should look like the image above ^
6: once this is complete depin the yellow connectors and solder them together as pictured


7:next take your w205 and solder your yellow wires to the points in the picture below


8: install your w204 chip and your freshly made harness and install in the w205 black housing (some modification maybe required, many people like to break away the sides, thats up to you)
9: install the w205 back cover
10: plug in your buttons, paddles and reinstall all other components and put the wheel in your car. connect the new airbag and youre all done

w204 facelift to w205

1: important that you have this style wheel buttons or this swap wont work

2: remove the metal airbag mounting plate from the new wheel along with your oem wheel
3: remove the black box from both wheels, and remove the chip hidden inside from both wheels
4: solder 2 wires to the points shown in the picture below (on the black box from the w205 wheel)

note: i soldered on pin connections on these wires to make the install easier but this isnt necessary
5: take your oem w204 chip. in the top left corner you will may have a set of 4 prongs, not all do, if its not there there will be 4 extra holes. you will need to insert/solder your new connections into these areas. please follow picture below for placement
note: if you have the prongs you can do one of 2 things.
1. use pliers and lightly grab and twist the prong to remove from the board and solder to your new wire (both wires)
2. solder your new wire directly to the prong already in the chip

this will take care of your horn.
3: flip the board and install into the black housing (some modification to the housing maybe required)
4: connect everything back to the board and reinstall in the wheel
5. install the wheel in your car


so thats it thats the proceedure for both style wheels. its not too hard, take your time, go slow


hope this helps anyone looking to upgrade to something new but doesnt want to pay for a custom made wheel
Im on mbworld a couple times a week, ill check back in on the post periodically.
for any immediate questions anyone is welcome to email me at rucarbon@outlook.com
happy to help
take care

 

It is a good idea to disconnect the negative battery terminal before starting the steering wheel swap. If you don't a SRS code will be set and you will need an advanced scanner or the dealer to erase it. Just good practice anyway when working on any electrical components or connections.

 

Hi I tried this and followed exactly. Paddles are backwards, and only one button works which is the wrong button response. Please help. 2009 C63, using a W205 C63 wheel.

 

I know this is an old thread, not sure how else to reach you. Followed all your steps for the pre-facelift model, and the buttons don't work.