Hello, just wanted to share some information regarding adding a Bluetooth module to the factory OEM Bose CDM. It is fairly technical, but is easily doable based on your experience with electronics and soldering. It may work for non Bose systems as well, however I do not know the differences at this time so I cannot say if it does or not. Before we start I know the Bose system is regarded as junk by most people on the internet, however I like the system and the nostalgia it provides. I know it’s not the best system out there compared to modern systems nor is it the best sounding so please no bashing in this thread. Information only.

There are several ways this could be done as well as just sending it off to be modded, but this is the way I chose to do it. Just wanted to share for fellow DIY members.

Supplies:

- Bluetooth Receiver. I used a $30 Logitech one from Amazon that works well, any receiver with an Aux port will work for this task.

- 12 Volt to 5 Volt Buck convertor. This I used to power the Bluetooth module.

- 12 Volt Micro Relays. 3 are needed. I used Bosch.

- 20-22 AWG Wire. I used solid core as it is easier to work with.

- 1N4002 Diodes. 3 are needed.

- Epoxy Glue. I used a two part epoxy.

- 60/40 .035 Solder.

- Soldering Flux.

Tools:

- Soldering Iron. Smaller tips work best.

- Small Wire Cutters.

- Wire Strippers.

- Hot Glue Gun.

- Isopropyl Alcohol.

- Hobby Knife.

Instructions:

1. This mod injects the Bluetooth audio signal into the CDM preamp into the same traces as the AM/FM Radio left and right.
2. Cut the two traces on the board that connect the AM/FM left and right signals to the preamp with a hobby knife. There are two solder pads on one side of the cut. Solder a wire onto each of them and connect them to two separate normally open relay contacts.
3. Next connect from the other side of the normally open contact to the solder pads on the other side of the cut. The Bluetooth module signal will connect at this point as well. Solder wires from the output of the Bluetooth module onto the board. There is also a ground point. (This allows the radio signal to work once the relay is energized. When it is not energized the Bluetooth will be the source as long as the radio input is on at the head unit.)
4. To power the relays you will use either a +12 volt external source or use the +12 volts ignition source that powers the CDM. There are two points under the black connector that can be used for this. (Don’t have pictures but the FSM shows the pin out of the connector.) Use an external switch to power the relays on and off. Each relay needs a diode across the coil if using the CDM power source.
5. Solder two wires onto the Bluetooth module switch and connect it to an external momentary push button switch for pairing. Connect the Bluetooth module to +5v power through the N.C. Contact of a third relay. The module needs a 12 Volt - 5 Volt buck convertor. This allows the Bluetooth to be turned off when the switch is flipped and the radio turns on.
6. I used hot glue to secure the wires in the CDM. I used the epoxy to hold down the relays. I used screw terminals to allow for the external switch connections. Make sure you use plenty of flux and clean the board with alcohol when done

Photos:

This shows the general layout of the CDM modification.

Here you can see where I epoxied the Bosch relays. The metal plate is removable. It covers the radio tuner. I used clamps to hold them while the glue cured.


Top left of the photo shows the 12 Volt - 5 Volt buck convertor.

I used screw terminal blocks to connect the outside switches.


Here is the Bluetooth module I used. I removed its external cases and used a screw and epoxy to connect it to the case.


Toward the middle of the photo you will see several red and green wires soldered to the board. The top set of wires will connect to both of the N.O. relay contacts. The middle set of wires you will solder the other side of the relay contact. You will cut these traces on the board between the two solder pads. This allows the relays to control the radio audio. The bottom set of contacts is where you connect the Bluetooth module.


Another good overview.

 

Congrats!

Very nice BT diy thorough documentation.

 

What year car is that CDM for. Does not look like any of the later 90 models of cars I'm familiar with.

 

It is out of a 1994 model. It has the Bose sound system.

 

Must be a different view could have fooled me. But now I recognize many of the components.

Were you able to get a schematic for the unit. I've been trying to get one for a long time.

 

No I wish I had one myself. Has to be one out there somewhere, just doesn’t seem to be accessible online.

 

Apologies for bringing up a dead post but would love some input - I've taken inspiration from your mod and I've spittballed designing a modular PCB that would sit inbetween the head unit (in the dash) and the Radio receiver (I *Think* this is the box in the rear storage compartment but I havn't checked - Unsure if the FSM is reffering here to that box OR the CDM unit that you've modified) - I'll find out when I start investigating). Below was taken from the FSM pages 1022-1028:





It shouldn't be too difficult to splice these wires and create the related Relay/BT Circuit in a neat housing. I'm assuming the traces you scraped in step 2 where the Audio In circuits that i've found in the wiring loom?

 

did you end up doing this at all?