I have an old Eclipse CD3100 headunit, which doesn't have an auxillary hookup besides a 13 pin din which is supposed to be used for iPod integration and a CD-changer. They also used to sell a RCA aux cable, but they went out of production long ago.
I have seen forum posts for making custom 13 pin din RCA cables and such, and I understand the basics (and have the supplies now). The thing I am confused about is how to safely determine which pins correspond to the left input, right input, ground, and the two wires to solder my switch to so as to let the head unit know there is something plugged in.
I have read to test the audio parts, I can sacrifice some old ear buds, cut the 3.5mm plug off, and just put the wires in different pin spots to see if the correct audio comes out. This would assume I have the switch or a solid wire hooked up already to let the unit go into AUX mode.
So, to get started, I need help safely finding out which ones I need to solder my switch to. From there I think I can determine the audio inputs through the method described above, and then I'm at a loss on how to find the ground wire for the audio.
Any suggestions? I have scoured the internet for pin diagrams for my headunit, and it appears they don't exist.