I have 2 connectors behind the radio slot: I believe the current after market radio was connected to the right connector, with nothing connected to the left one . What is the left one used for?

 

Welcome to the forum

You need to look at wiring color

2008 wiring below
Base model had amp in head unit
Deluxe had separate amp

 

Thanks!
THIS diagram matches the color / connector layout on the connector in the dash. I assume it must have plugged directly into the radio. I can now match up the new radio's pigtail to the male connector pigtail in the plug kit.

Thanks!

Dennis

 

Just as a HEADS UP
DO NOT USE the Green/orange stripe wire AT ALL on a Non-Ford radio............did I mention, DO NOT USE the wire from FUSE 22!!!!

That is the MUTE TO START 12volt wire, it only has 12v when key is turned to START position, that would MUTE the Ford Radio
If you were to wire that to a 3rd party radio for power then when you turn the key to ACC or RUN the starter motor would come on............lol, but not funny when it happens

So MARK IT as DO NOT USE, if you cut it then tape the end or cap it so it can't short

 

I had imdeed3d planned on NOT using it.. and just working it to the run/acc position... But hadn't considered the consequences if I HAD! Thanks for the tip to tape it off and tag!