My car came with a Blaupunkt 520 as the factory fit head unit. As it uses the on-steering-wheel controls, I don't really want to swap it out, but I do want to add the ability to plug a device into it such as a phone. The car had a CD stacker option, so my original idea was to find the inputs they would have used and add a 3.5mm jack.
After pulling the head unit out, I found the below sticker with the pin outs. Most I can figure out – FL, FR etc are the speakers, IGN is main power, 12V BATT is the memory, ILLUM is back-lighting and Earth is obvious. There are some there I'm trying to figure.
Using the information I have, does anyone know how to add an AUX input to this stereo head unit? I presume I need the TEL-AUX and maybe the TEL-MUTE. I have no idea what SDA, SCL, SDVC, MRQ, DIAG or SWC represent. I presume A-GND is an earth of some kind but not sure what specifically.
The first image shows the sticker on top of the head unit. The second is the receptacle in the car. You can see where some of the pins are not yet in use.
Best Answer
Pretty much most CD changer options on factory radios require digital communication to enable. SCL and SDA typically refer to I2C clock and data lines. Sdvc is possible voice control, swc is likely to be the wheel control. The middle eight pins are the four speaker outputs. Diag is diagnosis, mrq is likely to be an interrupt input? A ground could mean aux or analog ground.
That said, the picture of the connection harness shows its not wired for the voice option. Analog or aux ground, tel mute and tel aux have no contacts. The radio may support it but the wiring for it does not