I just acquired a 1993 SC400 and am planning to add Bluetooth and an aux in to the original Nakamichi stereo, whilst re-using the existing steering wheel controls for the obsolete (and already removed) phone system and re-purposing them to control the bluetooth module.

My current plan is to incorporate the CD changer/relay mod from PureDrifters thread with a 12V QCC3031 bluetooth board from eBay.

Parts list:
QCC3031 Bluetooth 5.0 Receiver Board (12V in) - $20
- $11
- $8
- $8
- $5
Connectors/Wires as needed
Total - $60(ish)

The board I plan to use uses momentary switches to control the bluetooth functions. My SC400 has the remote shown below already on the wheel. I've taken it off and confirmed that the switches on the board are momentary switches, so I plan to solder wires on to them and run to a 5-pin connector into the steering wheel, which I can then run to under the arm rest where I plan to put the bluetooth board. To tidy up I'll probably repaint it to add the correct symbols.

Note: There is a microphone in this control which I considered re-using, but the only bluetooth board I could find with mic in/out wiring didn't have an aux in connection as well, so I decided to go with an aux in over the microphone, as I rarely make/take phone calls when in the car. If you wanted to use the mic this CSR8645 board might work.



Wiring Diagram

The bluetooth board is on order from China so will take a while to arrive. In the meantime I plan to at least wire up the relay to an aux port in the arm rest, then I'll swap that over once the board gets here.

I'll try to update this thread as I go, any thoughts or anything I'm missing?

 

Ooh, that would be nice. Going to follow.

 

Looks really cool. Would love to hear an audio clip to see how the radio reacts to the Bluetooth.

 

if the bluetooth module can translate the inputs from the steering wheel controller, the rest of it is just wiring. Thats the only tricky part. This should work pretty well. Wiring wise its the same thing that im doing with a bluetooth module/controller built into one. Gonna be clean once its done though!

 

Whilst I'm waiting for the bluetooth board to arrive I've wired up the common lead for the switches. Each microswitch has 5 connections to the board, two on each side are connected all the time, and the sides are joined together when the switch is pressed.

Does anyone have any idea if the wires inside an ethernet cable would be suitable for the switch wires? I assume (maybe incorrectly) that they won't be carrying much current, and I have some Cat 6 cables lying around. Plus it would be easy to make a disconnect in the steering wheel using ethernet.

 

Well unfortunately I've just realised that all the wires running into the steering wheel are on a slip ring (seems obvious now I think about it), so no chance of me running extra wires into there. The board was originally connected by 2 wires so I may be able to do something with those. Possibly just hook up one button or maybe try and set up 2 arduinos (one in the remote and one hooked up to the bluetooth board).

On the plus side, I got the 4PDT relay hooked up and it works! I do have an issue with the right channel coming through both sides so I need to do some troubleshooting on that.