3rd harness wiring?
 

When installing an aftermarket headunit, does anyone know what the 3rd harness hooks up to?

The first 2 are the standard Toyota radio harnesses.

I can only presume that the 3rd harness (~20 pins or so?)is for:
- USB Hookup (4 wires)
- Aux Hookup (3 wires)
- Satellite radio Antenna?
- maybe for dual climate controls?!
- Subaru connector?

Okay, from what I remember, I really want to say that that 3rd harness looks like a factory 20pin subaru harness. Anyone have a pic handy to confirm?

This is the 20pin subaru harness.
http://img72.imageshack.us/img72/590...rspeakesq2.jpg

THe subaru harness pin wiring details is:
http://ae64.com/20-pin-pinout.htm

Can you post pictures of your your factory radio? (front, back, and label on the top or bottom)

What are the model numbers on yours (on the front and the label)? Does it have an FCC ID? You can use that to look up documents on FCC's site that often provides interesting pictures and information.

The Fujitsu Ten nav in 2012 Imprezas (front model number FW602US) is shown here, and the pin-outs are in post #9 below that, here. Does yours look exactly the same?

I included instructions on looking up the FCC documents in that pin-out post.

That HU actually has more than 3 harnesses, but the one you're probably talking about has 28-pins. It's mainly used for the aux input and microphone. It also has pins for SWCs, but I don't know if those will be functional on the BRZ and FR-S.

USB and antennas are all on separate harnesses.

You asked about this in ruskymx's thread (discussing retaining the USB socket), but I thought it would be better to answer here...

This thread talks about the mic in a 2011 Impreza:

Interface OEM Bluetooth Microphone with Aftermarket HU

Here's another about the 2011 Legacy/Outback mic:

2011 OEM Microphone in Overhead Console

Most aftermarket HUs use 2 wires for the mic. One wire provides DC power to the mic element and also carries the AC audio signal into the HU. The second wire is the ground/shield. It should be possible to use the aftermarket HU's mic power voltage to run the car's mic module (may require a few extra components -- resistors and capacitors).

First, someone needs to open up the mic module in a BRZ or FR-S to see what you're dealing with. There's a chance it could turn out to be a simple electret condenser microphone element (just like what aftermarket HUs have). But I suspect you'll find a module with an amplifier circuit, like in recent Subarus.