Car Stereo Aux Input Hack

After seeing a similar hack posted on hackaday I decided to give this hack a shot myself.  I bought my stereo back in 2001 before auxiliary in ports were mainstream in car stereos.  But in the last few years I've really wished I had one, but didn't really feel like upgrading a stereo in a 14 year old car.  So I was very excited when I found out there might be another option.

My stereo is an Alpine CDE-7859.  My goal was to figure out a way to bypass the fm tuner output and patch in the signal coming out of a stereo jack.  Using the example from the other post, this wasn't too hard.

For my first attempt I used a similar setup with the stereo jack that contained its own cut off switch.

First thing was getting the stereo out of the car.  Then dismantling the stereo to get at the circuit board.  The hardest part about this was taking off the cd player.  But the stereo itself was pretty easy to take apart.  I didn't take a picture of it, but locating the the FM module was pretty easy to find.  It was a seperate module wrapped in metal just Mukmuk found during his tear down.  But looking where the FM module was connected I found pins marked L, R, and Gnd.  So I was in business.

On my stereo the capacitors were surface mount, so I had a little less room to work with.  So next I used a Xacto knife to break the circuit between the pins and their capacitors.  And then with the help of my lovely wife I was able to squeeze in the four wires I needed to make my new circuit.  And the ground wire was off to the side so it was easy enough.

After that it was simple enough to wire up the the switch.

Only problem was that I forgot that I still needed to feed this thing through a hole.  Oops, I'm still new at this stuff.  So I had to take it off.  And then I put the stereo back together with the wires in place on the board.  Everything still fit fine.  There was even a perfect slot in the back of the stereo for the wires to come through.

I couldn't just put a hole in the front of my stereo for the Aux since my stereo has a removable face plate.  After installing the stereo back in the car it worked great, but after using it a while I decided that I wanted to change the design.  I wasn't happy with the aux jack being the functionality switch.  I decided I would rather just have a dedicated switch somewhere on the console to turn the Aux on and off.  And then I could just leave a cord semi-permanently attached to the jack.

So I ordered a switch I thought would work.  The hardest part was figuring out where it would fit on the console.  But I made it work.

After putting the console back together I wired it all back up.  It was pretty easy the second time.

And here is the hack in action.