Hello! I am new!
I am installing a new stereo in my girlfriend's '07 Fit Sport. I was hoping one of you kind folks could answer a few of my questions. I have installed stereos in my own vehicles before but they seemed a bit more straightforward than this. I ordered the following from Crutchfield based on their recommendation:

• Boss BE7ACP-C (link to manual: https://www.manualowl.com/m/Boss%20A.../Manual/634652)
• Metra 70-1722 Receiver Wiring Harness
• Metra 40-HD10 Antenna Adapter
• Metra 99-7872 Dash Kit

1. The back of the factory radio has 4 inputs. From left to right:
   Radio Antenna - I have the adapter for this to connect it to the new HU
   AUX Input - There was some adaptor plugged into this that let you hook up an iPod. Assuming I do not need the cables plugged into this now.
   Mystery Input - What is this one for? Do I need it?
   Main Radio Input - I have the Metra 70-1722 harness that connects to this.
   
   
   Can anyone tell me what that mystery input is that has the blue arrow pointing to it? (the white circle and line is from the stupid Crutchfield instructions, ignore that)
   There was a connector plugged into it but I cannot figure out what those wires go to.
2. On the main harness for factory radio, there is an Orange wire labeled 'Dimmer'. Does this connect to the Orange/White that is on the new unit labeled 'Illumination Input"? Or does that Orange/White need to be tied into the headlights somehow so that the new stereo dims when the headlights are on? And if that is the case, do I just not use the Orange 'Dimmer' from the stock setup?
3. There is also a Light Green wire on the new unit that is supposed to be connected to the parking brake. It says to connect it to the "power side of the parking brake" in the Boss manual. I know this is a safety feature but we would not be dating if she were dumb enough to watch videos while driving. Will grounding the wire be enough to bypass this? I saw something saying it needs a "pulsed" signal or something like that and they recommended buying some adapter from DIYbypass.
4. Any tips for installing the backup camera? It is supposed to mount to the license plate but I have not looked yet to see if that is even feasible with the back hatch door.
5. Best place to locate the microphone for the new stereo?

I know this is a lot of questions. The main one is if anyone can tell me what that mystery input was doing on the old stereo and whether I need to do something with it. the rest of the stuff I can figure out on my own but I was hoping someone that had done this before might have some tips or sage advice to save me some time.

Thanks!!

 

Replying with the same questions about mystery plug... Aux in and?

 

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