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?