Hello,
Just thought I'd add that I've had great success using these products to add Bluetooth (and therefore iPhone connectivity) to my factory BMW CD-43:
I think they came in the E-36. So it is BMW factory, just maybe a different generation. Still, it looks the business if you don't want the whole JDM light show in your cabin. And with the bluetooth mod I can listen to Spotify.
The way I did it in my E39 is with the german "BlueMusik" adapter.
It works if you radio is able to handle cd changers - a cd changer is just an aux input. It tricks the system, so it thinks that the audio is coming from the cd changer. Even the multi steering wheel works.
I'm putting a Blaupunk RCM104 in my e28 to do the same.
I did a DIY version of this in my e36 (C-43 radio) with an Amazon Bluetooth dongle. Spliced the aux L/R/GND wires from the dongle into the CD changer inputs for those channels on the radio and kept the CD changer data channels intact. Otherwise you have to trick it into thinking there's a CD available and it's playing to switch to the input. Then hard wire the BT dongle power. Honestly not sure the ROI of the DIY over just purchasing a ready product. I also added a ground loop isolator and extra radio ground because the alternator whine was noticeable, especially if you also had the phone charging from the car. Might not be an issue in the e28.
The CD-43 I believe came on Z3 models and maybe very late e36? Most e36 in the US got a C-33 or C-43. There is also a version that was installed in some Range Rovers of the era.
Sure. Let me start by saying that I am far from an audiophile (as evidenced by my hacking of an aux input into a stock radio) and there are probably way more robust ways to do this properly, but my setup just used one of these basic type devices that you plug the AUX into on its way into the radio. It did make some difference, but if you listened really hard, especially at higher volumes, you could still notice some alternator whine depending on RPM and such. I have also had somebody tell me that these "ferrite ring core noise suppressors" wrapped around power wires can help. However, I don't have any practical experience to comment on effectiveness and don't know which wires specifically you would need to put these around.
