Making 13 pin din -> 3.5mm AUX cable for Eclipse CD3100

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.

your best bet is to bust out a dmm and test the wires. unless anyone here has owned that exact head unit then that looks like your only option. thats all i can think of.

How would I even know what the readings correspond to? I've soldered and followed guides on making electrical components and stuff like this but I have never gone from scratch or used a DMM before :P

Wouldn't just buying this ECLIPSE INPUT HEAD PHONE JACK ADAPTER MP3 iPOD iPC-106 | eBay be easier? Or ECLIPSE AUX-105 3.5MM 1/8" AUDIO JACK INPUT iPOD MP3 | eBay

I read that the one from Hong Kong actually wasn't designed for the eclipse headunit or something on a couple of websites, with people saying that it either had an incredible amount of interference or flat out didn't work. The other one I hadn't seen before as all cables officially made for the iPod integration hooked up to a box that also had a weird cable input.

I might have risked it but I ultimately just bought the little male 13 pin din cable and some heat shrink tubing, so if possible I'd like to use it.

I've tried googling how exactly to use the multimeter for this purpose but most of the time people are just saying "use the multimeter to determine the pin placements." I don't actually know what to look for or what setting to use to do this though.

In all, it would be easier, but I've bought the stuff and would like to continue, so if anyone can link or explain how exactly to use the DMM in this case that's really all I should need.

Thanks

I found out how to make the wire. I ended up just plugging in the incomplete male din, and testing one of the audio wires hooked up to a cd player I didn't care about. My care also has an AUX mode hidden in the menus, which once enabled let me cycle into aux mode past CD and FM/AM. Apparently the switch I bought wasn't needed because of this AUX channel (I had been following roughly the guides for several different aftermarket head units).

Anyways, after testing and figuring out which pin was the left and right audio, (spaced apart perfectly like other headunits so I figured the one in the middle had to be ground, just like the other units), I soldered away, drilled a little port in the aftermarket box adapting kit for the wire to go thru, made a little grommet plug out of electrical tubing and electrical tape so the cord can't be yanked, and there we go.

If for some reason someone else is searching and doing a similar thing, the pin out I used for my Eclipse CD3100 is here:
-/----13-----\
/--9-10-11-12\
\--5--6--7--8-/
-\-1--2--3--4-/

8 was left audio in, 6 was right audio in, and 7 was ground.

It works perfectly with no interference :D

Thanks for the DMM suggestions and stuff guys. I would have used one if my dad's I found in the garage wasn't broken.