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 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 choosing. I recommend that you have a professional installer do the work unless you have sufficient knowledge to do your installation.
Section 1 – Swapping out the OEM head unit for the AHU
Part A – Removing the OEM head unit.
- 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 W220.ee site has some pretty good fuse diagrams here: https://w220.ee/Fuses
- You will want to put the ignition key in, put it in the start position (but do not start the engine), apply the parking brake, and put the gear shifter in the drive position.
- 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.
- 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 then close the ashtray and pull it the rest of the way out.
- 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.
- Put the car back in the park position, and remove the ignition key.
- 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.
- 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.
- 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.
- 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.
- 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
- Examine the connector that went to the COMAND unit. The connector on mine is actually composed of 2 plugs that plug into 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.
- Depending on the brand of MOST optical encoder/decoder you bought, there may or may not be an adapter housing that the MOST connector will need to be placed in first, then it needs to be plugged into the MOST adapter.
- 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.
- 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.
- 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.
- 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.
- 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.
- Connect the AHU wiring harnesses to your AHU.
- Reconnect the HVAC wiring harness plug to the HVAC unit.
- Reinstall the fuses you removed earlier in Part A.
- If your AHU had some shipping screws installed to keep the CD/DVD drive from damage, now is the time to remove them.
- 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.
- Turn on the ignition and see if your AHU is working properly. You might not have a 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.