How I Installed Bluetooth in my Car Stereo

[This article was written Sept. 5, 2023. If you are working on a similar project, leave a comment.]

There are a ton of videos and guides about how to retrofit your old car stereo to get Bluetooth streaming, but I’ve decided to share my own experiences with this, since my situation is a little bit unique. I also wanted all my notes (thus far – it’s a work-in-progress) to be in one place.

Background & Context

I love my Volkswagen 2011 Golf and it’s head unit (car stereo), the RCD310. The unit has a simple design, but the attention to the fine details is what I fell in love with. For example, the two knobs control volume and the radio frequency, just as they should! No button mashing if I want to change stations.

The look of the unit is clean. The text is easily readable without using a bright LCD screen. In the dark, the display glows a pleasant ocean blue, and the buttons match the OEM red glow of the rest of the car.

It communicates what I need to know. Nothing extra, nothing fancy or distracting while I drive. I can enjoy my ride without needing to check where I am in the FM range. I don’t need a VW GPS screen or some gawdy interface when I can just stick my phone on the dash and use Google Maps.

The problem with the RCD310 is that it doesn’t come with Bluetooth.

I Demand Bluetooth

The RCD310 sometimes ships with Bluetooth installed and ready to go – mine did not, unfortunately. So far, I’ve dealt with this by playing audio through the AUX input. Since I have a newer iPhone without the headphone jack, I need a lighting to AUX adapter. It also means more wires and more points of failure. More wires while driving stick, well that’s just unacceptable.

I could’ve easily paid a few hundred dollars to swap out the RCD310 for something more advanced with Bluetooth, but nothing I’ve seen matches those wonderful design details above. Therefore, the project objective became to add an aftermarket Bluetooth device to the car. However, after placing my order, I made the project more complicated by requiring that I keep the AUX input intact. In other words, I cannot simply replace the AUX input with a Bluetooth input.

Project Requirements

  • Audio can be streamed via Bluetooth to the Volkswagen 2011 Golf.
  • Bluetooth functionality comes via the OEM head unit, the RCD310, because it’s so simple and beautiful and I love it.
  • Bluetooth functionality cannot disable any existing features, such as AUX input or the stock CD player.
  • The Bluetooth device must be powered by the car battery.
  • The Bluetooth device must only have power when the car is turned on (i.e., it must not drain the battery when the car is off).



  1. Connect the BT unit to the RCD310’s inputs.
  2. Connect the BT unit to the Cigarette Lighter for power.
  3. Enable BT audio (note, I’m stuck on this step).

The Work

Prep the Bluetooth Module

First I extended the power wires on my Bluetooth module. I needed them to be long enough to reach the cigarette lighter’s power cables. I did this by soldering another 12 inches of Primary wire to the power cables on the Bluetooth device.

Next, I removed the Head Unit. There are plenty of videos on how to do this, but in a nutshell, pull off the trim with the removal tool, unscrew the Torx screws, yank out the head unit, and then remove all plugs to it so you can pull out the entire unit. (Note, I did not run into any issues with ‘SAFE’ or needing to reboot the unit with a code).

From the RCD310’s quadlock connector, I unplugged the little blue brick. This brick contains the audio wiring for the AUX-IN. At this point, I found that the blue brick was not the same size as the white brick that shipped with the Bluetooth module. So I could not simply swap the Blue for the White – I would have to physically remove the 3 wires from the Blue brick and replace them with the 3 wires from the White brick, in the correct positions. This made me decide to keep my AUX intact, because once I pulled those wires, I might not have been able to easily get them back in. So I began to look at other options.

Research the CD Changer

I learned from a Youtube comment that it might be possible to connect my BT to the inputs for a CD changer (like one of these). This was further confirmed as a possibility by Hackaday, so I decided to attempt it before replacing my AUX-IN with BT.

The RCD310 pin out diagram indicates there are pins for a CD changer. My car does not have a CD changer, so I might be able to put my BT inputs there. This would let me preserve my AUX-IN.

Of course, it might not work. The RCD310 and the Golf are integrated in a some ways I don’t understand, for example I can change radio stations using my cruise control buttons. I think this is done through what’s called the Multimedia Function Interface (MFI).

My fear is that the RCD310 will be expecting a CD Changer signal – something digital that tells the head unit, “Yes, I am a CD changer, and I am legit, and right now I’m ready to play track 2 from the CD in slot 3.” If this is how it works, then I am not sure I’ll be able to make this happen without something mega complex like an emulator.

Next Steps

I have the BT device powered up. My phone connects to it and streams to it. The BT is only on when the car key is turned to Accessory mode, so it’s not draining the battery when the car is off. The BT wiring is attached to the CD changer inputs.

But there is no output from the RCD310, no music, no audio, and no option to select the CD changer.

My next step is to enable option on the RCD310’s menu to switch to “CD EXT” or “CDC” to listen for input from the CD Changer. To do this, I need to find someone who knows VAGCOM or a similar interface. This person might be a hobbyist or a technician at the dealership. Whatever the case, this method can hopefully reprogram the RCD310 to enable the button option for the CD changer in its menu. Then, I can experiment and find out if the BT audio plays or not with this option selected.

I’ll update this post if/when I get there. For now, I have my faithful AUX for my long road trips.