Newbie with a question here.. I have searched several forums, and can't find an answer to this one. I just bought a 1998 A4 with no stereo. I don't believe it had Bose or even symphony. The area where the stereo goes was empty with a few cut wires. I've pretty much got it all figured out EXCEPT for a single slim 1/2" x 2" circuit board plugged into a 2 wire (white and orange) connector. I have no clue what it is, or where it's supposed to be attached. Any ideas? TIA

 

Welcome to the forum.

The Symphony system is Bose. It's their top of the line model (it goes Bose, Bose Concert, Bose Symphony).

I can't remember if I had the same box & 2 wires on mine (I have the symphony system), but I have a couple links here for you that may help. Check them out and let me know if they help you solve your mystery.

I'd don't want to pull my head unit out right now (strictly because I'm being lazy), but I will if I have to. I know that some of the wires and harnesses weren't even required for my install.

Try hooking everything up w/o those wires connected (but don't let them ground out). If everything works fine, **** it. Keep it movin'. If it doesn't work properly, take a DMM and see if either wire is putting out any voltage (with the ignition on).

You should also check to see if you have an amp. It you do, it will be in the trunk, behind the drivers side body cover. If you have an amp and component speakers in you cabin, you most likely have a Bose system. You can pull the part number off of the amp and cross reference it with ebay (or wherever) and find out exactly what you have and go from there.

If you still can't get everything resolved, let me know and I'll pull my head unit out and check for you.

Here are the links:

Metra Online | Welcome to Metra Auto Parts Online Warehouse

Help with B5 S4 Install | Audi Forum

G/L

 

Thanks for the reply. I look forward to reviewing these links. Im just not sure it's a part of the audio. I've never seen a circuit board unplug with its own wiring harness. I have a pic of it, but don't have a Host for the pic.

 

 

 

Circuit board in question is a lilt to the left of center...

 

Yeah, that's weird for that board to be exposed like that. I doubt it's stock. I can't help but notice that it looks like it's already plugged into something. Is it? Does the wiring integrate into the factory HU wiring harness? If so: is it spliced in, or does it look factory? Did you try the new HU w/o involving that piece? If so, what happened?

Looking at the pictures, with the limited view I have of it and not being there to mess with it in person, I'm thinking it goes to something like a dimmer switch, or it could be wiring that goes to the mute feature of a hands free phone setup, or possibly the vehicle speed to volume matching feature, but I'm pretty sure that's set in the HU itself.

If you can, see if either wire is hot (has power) with the ignition off. If so, start pulling fuses that are relevant to those items until it loses power. If one or both get power only with the ignition on, do the same thing and if you can find the fuse that kills the power to either wire, you can find the circuit it belongs to and go from there. That way, you don't need a DMM (if you don't have one). You just need a 12V test light.

LMK how it goes. G/L

 

Thanks for the reply. I will investigate more when I get the chance. Here are a few more clues. When the key is on, it is getting about 5v and about 575 resistance. Here are a few more photos. I'll try the fuse block later today.


And this is the wiring harness that it was plugged into:

A little blurry, but it's a rounded off plug.

The mystery grows...

 

It's your Interior Temperature sending unit (part of the climate control system). It has noting to do with your stereo install.

Here, this is the cheapest one I could find: Temperature Sensor OEM 4B0 820 539 - 02-13 Audi A4 A6 A8 VW Golf Jetta Passat

 

Ahh, I could see that. i guess the logical location to plug it into would be the small "horn" looking outlet just below the stereo.