Stock Radio with aux input

I got a bug to install a factory radio. The original stereo had broken awhile back when my Dad still owned the car and he has installed a new head unit with CD. I was okay with losing CD ability (and picking up tape ability!) as long as I could add an aux input. My Dad had added an input to the original stereo so we knew it could be done but any documentation on the mod was lost so we had to start from scratch. I picked up a radio in great shape from a fellow board member and we got to work.

We were able to power the radio with a DC supply and probe around with the oscilloscope to see where the audio went and where might a good spot to tap our own signal in.


We ended up using the 3 pin connector seen at the bottom of the picture above. Running two wire pairs out of the back of the radio I am able to use a switch to control which input the radio sees (my aux input, or the radio/cassette input).

This should be a short video of the switching in action.

The final install of the switch and radio should happen tomorrow 🙂

Well I had an issue with the left channel dropping out on the radio (unrelated to the aux input mod) so I had to trace the signal back through the left amp and reflowed a few connections on the amp and also the volume control. After all that the left channel seems to be working much more reliably.

Old new stereo

New old stereo

I got the radio installed without much issue. On the driver’s side pop-out (on the left below the radio) you can see a very subtle switch. This is what switches between the radio/cassette and my aux input. On the right in the back you can see the floating 3.5mm jack. Instead of mounting it somewhere I left it as a cable so I can tuck it away if I want.

Also a few of these showed up in the mail today from Amazon. Having the aux input really eliminates the need for cassettes but I think it will be fun to have some in the car.