How to install Bluetooth (BT) in the BMW Business RDS radio (C23)
⚠️ IMPORTANT: You perform all modifications at your own risk. I am not responsible for any damage or mistakes made during the process.
Items required for an easy & successful installation:
- DIY Bluetooth kit for the BMW Business RDS Radio
- Solder, soldering iron, flux, IPA/PCB cleaner, desoldering pump etc.
- Torx T8 screwdriver
- Flat head screwdriver
- 3mm drill
- Hot glue
- Scalpel
- Wire strippers & cutting pliers
1. Remove both top and bottom lids using the flat head screwdriver:
2. Pull the volume button off. The front panel is held by 6 plastic tabs – 4 at the corners and 2 in the middle. Start by pushing them in one by one and at the same time push the front panel slightly forward and keeping the pressure, otherwise they would just pop back in. Use the flat head screwdriver to release the middle parts. I recommend to start from the side that is close to the arrow buttons:
3. Undo 4x T8 bolts holding the tape deck mechanism and disconnect its two connectors simply by pulling them up. Take it out and also remove its bracket that is held by 2 more T8 bolts:
4. While you are already there check that these 2 retaining washers at the end of the radios locking bolts are still there. Usually they fly off if over-tightened… Push them back in place:
5. For the microphone input drill 3mm hole and use metal files to get rid of the rough edges. If you also bought preamp outputs with this kit then here is a guide of how to install them.
6. With scalpel carefully scrape off the isolation from these 5 contacts shown on the photos. If any of them are full of solder use desoldering pump, it makes your life easier later when you have to pass through the wires. Carefully make 3 cuts to disconnect the 3 tracks without damaging the others that are very close. You can double-check whether they came out successfully and if these 5 contacts are empty simply by looking the PCB against the light:
7. Some radios have slightly different main circuit board layout (marked as 3455 instead of 3444) and usually they are covered with layer of amber colored protective resin. In order to solder anything there it needs to be scraped off. The rest is like was in the previous step. If needed you can use needle with pliers to empty these 5 contacts from the resin or if there is solder, you would have to use desoldering pump.
8. Scrape off the isolation for the ground connection and bend that component out of the way:
9. Pull off these 2 capacitors and de-solder what is remaining.
10. This light blue capacitor needs to be on the same level as its neighbors so the controller could fit inside the radio. It moves only few millimeters at a time so you would have to solder and push each side multiple times:
11. Insert the controller, shorten the wires and tin the ends:
12. Solder the wires like on the photos, if you don’t plan to use the radio with MF-steering wheel then you can leave the IB wire disconnected. Microphone input: red wire goes to M+, black to G (ground).
Use a piece of leftover wire (cut earlier) for both the EN wire and the resistor. Measure the required length, wrap it around the resistor lead, solder it, trim the excess, and slide heat shrink tubing over it as illustrated below:
13. Clean the flux residue everywhere you soldered:
14. Temporarily install the controller and position it so that it doesn’t touch or short out any components. Then reattach the front panel and switch on the radio. If nothing appears on the display, then something went wrong during assembly and you’ll need to look for the issue. Go back to step 12 and carefully double-check all connections — most likely some wires were mixed up (or your radio is one of the rare units that are not compatible):
If the radio turns on normally then go to your smartphone Bluetooth settings, search for available devices and pair with the ”BMW Business RDS”. Play some music and increase the Bluetooth volume level from your phone so it would match with the FM level, then there won’t be any noticeable difference when you later switch between these modes:
15. Secure the wires and controller with hot glue, also make sure the controller doesn’t stick out from the radio, otherwise you can’t install back the top lid:
16. If you didn’t buy the volume regulator encoder with this kit then skip this step. For the replacement, first remove the nut holding the encoder and then pull up its connector. De-solder it from its small PCB (I usually heat up all 3 legs together and tilt the back end down and then repeat it with the remaining 2 legs until it’s off) and use solder sucker to clean the holes. Installation is in the reverse order:
17. Re-solder all 14 front panel connector pins as they often come loose, when it is pulled off. Run the BT antenna cable through the hole. Align the antenna connector with its socket and use flat head screwdriver to push it in as it needs quite some force:
18. Clean the tone head. Move the wires to the side, out of the way and reinstall the cassette mechanism. Place the antenna between the front panel circuit boards, exactly like is shown on the photo. When installing the front panel back, make sure that the antenna cable doesn’t get squeezed in between and all, whats left over, will be inside the radio:
WELL DONE! You have earned the chocolate 🙂
