Stereo electrical issue not covered by the faq.
 

I recently picked up a 1986 rx7 and the previous owner tried to install a cd changer, but since the attempted install the stereo has never worked.

I am working on getting the wiring back to stock the best I can. There was a wire running from the cd changer control box to under the dash spliced into a connector right near the steering column.

https://i.imgur.com/uqL7QfL.jpg

picture for reference. Does anyone know what that blue-red wire controls?

It should be ACC power, Amp power, or Antenna power from the ignition switch. Wiring Diagram is here RotaryHeads.com - 2nd Gen RX-7 PDF Technical Manuals FC3S. Check for +12v from ignition switch.

Thanks a bunch. I was able to get everything fixed on it. I pulled a ton of wire that the previous owner ran under the dash. Using crimp butt splice connectors I got the electrics looking decent as well.