Android Head Unit Installation

I did this installation myself on my 2004 Mercedes S430 4matic.  My car is equipped with the Bose amplifier system that utilizes the MOST fiber optic system.  Your car may or may not be similarly equipped.  These instructions are what I did to make the transition to an Android head unit in my car.

This installation process will take anywhere from 4 to 6 hours for your average W220 owner to accomplish.  This is assuming that your W220 has not had its wiring or anything else done to it that will impede the installation of the radio.  That also means that the car is also free from having a lot of stuff stored in the cabin and trunk areas.

I strongly recommend you read all the way through this guide before starting the process.  I give reasons for why I do things a specific way or why I installed extra wires while doing the installation.  Reading through all of this doesn’t take long and may save you some headaches later during your install.

(I will be posting more pictures in the near future when I have the time.)

My car came with:

COMAND by Mercedes-Benz/Siemens VDO using the MOST fiber optic system, part # A220 827 4242 ZGS 000.  The car’s stereo system is also equipped with the BOSE amplifier and speaker system (option 810).  There are a total of 3 wires plus 2 fiber optic lines going into the head unit.

I replaced it with this:

Rockchip PX5, my particular version is sold by Seicane and is their S127509 unit. There are multiple vendors of this particular style of an Android head unit aka AHU, just use a search engine of your choice to look for what you want in particular.  The procedure I’m detailing is general enough that you don’t have to buy the exact same model AHU I did.  An extended length radio antenna wire was included with the purchase by the vendor.

The default launcher works well, but choosing a different launcher that works well for your needs or esthetic desires may be an option you’ll want to exercise.  I installed a different home screen launcher called CarWebGuru on my AHU.  I found it to handle all my needs while also giving me a lot of flexibility in its appearance.

Disclaimer:  I am describing the process by which I replaced my OEM stereo head unit with an Android head unit in its place.  I do not imply that this process will work for you.  You are responsible for your own actions and any damage that may happen to your car, its radio, or its systems is entirely your responsibility and not mine.  I do not represent nor should it be construed that I endorse any of the merchants, vendors, or companies whose products are referenced within these instructions.  I am giving the links to various entities because they are where I found the items I needed to complete this project.  You are free to go to any supplier/vendor of your own choosing.  I recommend that you have a professional installer do the work unless you have sufficient knowledge to do your own installation.

In addition to the AHU, you will need the following items for a clean installation:

Optional items:

Tools needed:

  • Torx screwdriver set
  • Metric socket set
  • Panel & trim prying tools
  • Wire strippers
  • Phillips #2 screwdriver
  • Barrier terminal blocks (example) or T Tap electrical connectors (example)
  • Soldering iron & electrical solder
  • Dental pick or very fine icepick tool
  • Fish tape for pulling wires (or a sacrificial heavy gauge coat hanger)
  • Good quality electrical tape (better yet, rubber electrical tape)
  • A good quantity of small zip ties
  • Dielectric grease

Although I have not used the following items myself, I have been told that it will be of interest to those who have a different setup than what I have in my car.  A shoutout to my Facebook friend Tariq Shawan who uses these components on his car (which is equipped with the D2B fiber optic system) for the following information:

  • Optical fiber adapter for D2B optical systems.  I have been told that this particular fiber-optic adapter will work with Mercedes cars that are equipped with the D2B fiber optic systems.  I strongly recommend confirming it with the vendor since it is labeled as a MOST adapter and not as a D2B adapter:
  • Carlinkit USB CarPlay Dongle (hard connection between phone and AHU):
  • Carlinkit Wireless Smart Link Dongle (wireless connection between phone and dongle, dongle is hard connected to the AHU):

If you are fitting an AHU to an earlier model COMAND head unit, you may also need to source the appropriate oem wood trim pieces.  Usually the AHU’s vendor will supply plastic trim pieces that work but don’t quite feel or look as though they came with the car.  I suggest eBay or other suppliers such as auto-breaking yards that can supply genuine oem trim pieces.  A quick search using your favorite search engine will bring a great number of sites to find these parts at reasonable prices.

Before starting the changing of the radio from the OEM head unit (COMAND) to the AHU, I cleared/removed all of my media from the car’s radio system.  That includes any cassette or compact disc from the OEM head unit and the navigation disc and the compact discs from the trunk units.  If nothing else, remove the disc & cassette from the OEM head unit.  Once the OEM head unit is removed, there is no easy way to remove the media from the OEM head unit.

I chose to strip back some of the insulation and use terminal blocks to make my connections to the car’s wiring.  Alternatively, by using T Tap connectors, you can easily ‘tap’ into the wiring in place of stripping back the insulation like I did.  The way I did it allowed for the easy application of dielectric grease to prevent oxidation or corrosion in the connections.  The choice is yours, both methods work.

Section 1 – Swapping out the OEM head unit for the AHU

Part A – Removing the OEM head unit.

  1. Pull the fuses that control the radio system and ashtray cigarette lighter of the center console of the dash.  You’re going to be playing with electrical wires and the last thing you want to do is permanently damage your car’s wiring or electronics due to an electrical short.  While you’re at it, pull the fuses related to the center front cigarette lighter because you will be tapping into that cigarette lighter’s power leads also.  The site has some pretty good fuse diagrams here:
  2. You will want to put the ignition key in, put it in the start position (but do not start the engine), and put the gear shift in the drive position.
  3. Open the ashtray and remove the 2 Torx screws at either end.  Put the screws in a safe place – the ashtray (if clean & empty) is a great place to store them temporarily.
  4. Gently tug at the ashtray and it will slip out of the center dash console. I found that after it initially comes out, that it is easier to open then close the ashtray and pull it the rest of the way out.
  5. Disconnect the power connector at the back of the ashtray unit and place the ashtray either on the seat next to you or the floorboard.
  6. Put the car back in the park position, and remove the ignition key.
  7. At this point, the climate control panel (HVAC unit) will practically pop out of its location with a gentle tug.  The HVAC has a cable attached to the back of it.  You will need to disconnect it by pushing down on the release portion of the plug while moving the catch lever so that the plug & cable is released from the HVAC.  Place the HVAC next to the ashtray.
  8. Use a panel/trim prying tool to remove the upper wood trim piece from the center dash console. You do not need to use a lot of strength and be careful not to mar the dash or trim piece while removing it.  I found that if you gently work at the right end of the trim piece, it will come out.  Do the same to the left side and it will pop out.  Place it with the HVAC & ashtray.
  9. Remove the lower 2 Torx screws and then remove the upper 2 Torx screws. The radio will stay in place if you don’t pull on it.
  10. While holding the OEM radio from underneath, gently pull on it and it will come out of the console. Do not let the radio’s weight pull on the wiring connected to it.  You do not want to damage the optical fibers.  They are a major pain to repair/replace if they get damaged.
  11. Disconnect the connector in the back of the COMAND unit. The COMAND unit is now free of the car.  Place it where it will be safe in case you ever decide to reverse the AHU installation.  I put mine in the box my AHU came in.

Part B – Connecting and installing the AHU

  1. Examine the connector that went to the COMAND unit.  It is actually composed of 2 plugs in a housing that keeps them together.  You will need to slip the MOST fiber optic connector (the one with the 2 orange wire-looking lines) out the housing.  There’s a release near the back of the plug that when pushed aside, the MOST connector can and will easily come out without any effort.
  2. Depending on the brand of MOST optical encoder/decoder you bought, there may or may not be a housing that the MOST connector will need to be placed in first, then it needs to be plugged into the MOST adapter.
  3. Stripping back (but not cutting) some of the insulation on the positive (+) and negative (-) wires on the console end of the ashtray wiring, you will then need to connect the positive wire coming from the MOST adapter to the positive wire of the ashtray wiring, then connect the negative coming from the MOST adapter to the negative wire of the ashtray wiring.  You can connect the wires by either soldering or using a couple of the terminal blocks.  Either way, wrap the connection in electrical tape to properly protect the connection.  Use dielectric grease on the connections if you do not solder them.  This will prevent the wires from eventually corroding and losing a good connection to each other.
  4. In some cases (like mine), the main power leads going to the AHU are part of a larger plug.  Using a dental pick or a fine icepick style tool, you can gently coax both the negative (-) and positive (+) power leads out of the AHU’s wiring harness plug.  If you’re lucky enough to simply have plain wires without some kind of plug on the non-AHU end of the wiring, ignore this step.
  5. Stripping back (but not cutting) some of the insulation on the positive (+) and negative (-) wires of the wiring harness plug that originally went to the COMAND unit, you will then need to connect the positive (red & yellow) wire coming from the COMAND plug to the positive wire of the AHU’s wiring harness, then connect the negative (brown color) wire coming from the COMAND plug to the negative wire of the AHU’s wiring harness.  You can connect the wires by either soldering or using a couple of the terminal blocks.  Either way, wrap the connection in electrical tape to properly protect the connection.  Use dielectric grease on the connections if you do not solder them.  This will prevent the wires from eventually corroding and losing a good connection to each other.
  6. Examine closely the connector that was attached to the HVAC unit.  You should notice a pair of wires that are twisted together.  One should be brown, the other brown & red.  These are the canbus network wires of your car.  Stripping back (but not cutting) some of the insulation of these two wires, you will need to connect the green wire coming from the canbus adapter to the brown & red wire of the HVAC unit’s wiring harness by either soldering or using a couple of the terminal blocks. Either way, wrap the connection in electrical tape to properly protect the connection.  Use dielectric grease on the connections if you do not solder them.  This will prevent the wires from eventually corroding and losing a good connection to each other.  Do the same with the green & black wire from the canbus adapter connecting it to the brown wire of the HVAC unit’s wiring harness.
  7. Examine closely the wiring harnesses of your AHU.  One of the wiring harnesses will have RCA connectors on it designated as FRONT OUT Left (or L) and FRONT OUT Right (or R).  The left plug should be a white one and the right plug should be a red one.   Those will plug into the corresponding connectors of the MOST adapter.  I recommend wrapping some tape around the plugs after the connections are made.  This will prevent them from coming loose.  A very small dab of dielectric grease can’t hurt either on all the connections to prevent a bad connection due to future oxidation or corrosion.
  8. Connect the AHU wiring harnesses to your AHU.
  9. Reconnect the HVAC wiring harness plug to the HVAC unit.
  10. Reinstall the fuses you removed earlier in Part A.
  11. If your AHU had some shipping screws installed to keep the CD/DVD drive from damage, now is the time to remove them.
  12. Place the AHU into the center console where the COMAND unit was and reinstall the upper 2 Torx screw to hold the AHU in place (and safe).  Don’t worry about reinstalling all the other screws yet.  You’re going to have to remove the AHU at least one more time if all checks out and more than that if it doesn’t.  Tuck all the wiring, the MOST adapter, and the canbus adapter into the back of the center console area and, if you can, up behind the AHU to keep all of the stuff out of your way.  Place the HVAC unit back in its proper location so that all the stress is taken off the wiring connector.  No need to reinstall the ashtray assembly at this time.
  13. Turn on the ignition and see if your AHU is working properly.  You might not have good radio reception due to the antenna not being hooked up and the same for the GPS.  But you should be able to hear something using the CD player or Bluetooth.  You will need to pair up your phone using Bluetooth before trying any of the Bluetooth features to double check.  Make sure your volume and phone controls work on your steering wheel as they should.  If anything doesn’t, then either one of your connections is bad or you might have a defective component.  If it’s not working properly, go over all your connections carefully before getting ahold of your AHU’s vendor.  Worst-case scenario, reverse all the Part A & B steps to reinstall your COMAND radio and you’ll be back to using your OEM setup.  This is why I said NOT to cut the wires.  It makes it easier to restore the car stereo system to stock if you need to or want to resell the car without the AHU installed in it.

Section 2 – Running the needed wires from the AHU to the trunk area

Part C – Running wires from the trunk area to the AHU

You will need to remove the center arm console, the rear seat (seat bottom & back portions), the rear trim trunk panel, and the side trim panel in the trunk where the stereo components are located.  On my car, it was on the driver’s side (USA spec).  At this time, I’m not going to go into detail about the removal of the console, rear seat, and the trunk’s trim panels because there are a lot of examples on YouTube and on the internet in various forums.  I will eventually, but not right now.

  1. Having removed the above-listed components, you should now assemble your remaining extended length wires (radio, rearview extension cable, GPS, etc) into a cable.  I strongly recommend that you include the rearview extension cable at this time because having to run it later is very time-consuming.  The cable is about $7 or $8 and the hassle to run it now is priceless when it comes to sweat and aggravation.  Starting at the end which will eventually have connections to the AHU, use a small zip tie about every 6 inches until the entire cable is assembled.  I recommend cutting the excess plastic off the zip ties to make it easier to run through the car.
  2. Starting inside the cabin and using the fish tape (or heavy coat hanger wire), pull the AHU end of the cable under the carpet from the rear seating area to the shifter area.  Pull enough of the wiring to give yourself about 8 to 12 inches of slack so that it will reach the AHU and have enough cable to spare.
  3. Thread the cable from the rear seating area to the trunk.  I found that I had to temporarily remove part of the back portion of the door seal along with a little bit of plastic trim along that area to find a spot to thread the cable through to the trunk.  It’s not glued in and can be easily pushed or snapped back into place afterward.
  4. Thread the cable to the stereo component area.
  5. Remove the carrier that holds the navigation unit and the multi-CD player from the car’s chassis.
  6. Disconnect the GPS Fakra connection cable from the back of the navigation unit and plug the cable into the corresponding connector of your cable.
  7. Disconnect the radio antenna Fakra connection cable located at the top of the audio gateway (AGW).  This is the component directly below the multi cd player and closest to the spare tire.  The connection cable you’re looking for is connected to the upper connector on the AGW and is black.  Connect that cable to the corresponding connector of your cable.
  8. Secure all the wires out of the way and reinstall the carrier that holds the navigation unit and the multi-CD player to the car’s chassis.
  9. If you plan to install a backup camera, now is the time to do it.
  10. Reinstall all the seals, the trim, the rear seat, and the center arm console.  You are now done in the trunk area.

Section 3 – Connecting the cable to the AHU

Part D – Connecting the AHU to the wires going to the trunk.

  1. Remove the 2 Torx screws holding the AHU in place and gently remove it out of the console.
  2. Connect the radio antenna portion of the cable to the AHU.  It should plug right into the back with no troubles and just as a ‘normal’ radio antenna cable would.
  3. Install the Fakra to SMA (or GPS-type connector) adapter to the GPS connector on the AHU.
  4. Connect the Fakra to SMA (or GPS-type connector) adapter to GPS portion of the cable.
  5. If you ran the rearview extension cable, then connect the yellow RCA plug to the BACK VIDEO IN wire on the AHU’s wiring harness.  Sometimes this extension cable comes with a red wire, I do not recommend you connect it to the AHU at this time unless you are currently installing a rearview camera.  That wire has the potential to feed 12 volts through it and unless your backup camera requires it for power, it’s one less thing to go wrong if it’s not connected.
  6. Turn on the ignition (no need to start the car, just all the accessories).  The radio portion of the AHU should now get much better reception. Check to make sure that the AHU now sees all the GPS satellites it needs to operate.  You may need to start and move your car into an area that the overhead is clear in order to get a GPS signal.
  7. Depending on if you are or aren’t planning on using any other portion of your AHU wiring harnesses (like the USB, Video-out, etc), now is the time to get it done and run the wires to where you want.  Think about how you are going to get your phone to hook up to your AHU whether it is using Carplay or a wifi hotspot.  That is up to you.
  8. Reinstall the AHU into the dash.  Start with the upper Torx screws, but leave them a little bit loose, then install the lower Torx screws.  Once everything lines up, tighten all 4 of them.
  9. Reinstall the trim piece that goes directly above the AHU.
  10. Reinstall the HVAC unit.
  11. Reinstall the ashtray in the reverse manner that you removed it.  (See Steps 2 through 5 of Part A)
  12. Enjoy your Android radio.  I enjoy mine.

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