Re: Wiring

[Jay@aol.com]

In a message dated 96-10-15 11:14:41 EDT, APOWELL@agcom.tamu.edu (Al Powell)
writes:

> > Top section: What is U(B)+?   
>  
>  I think it's (unswitched Battery +) but this is a guess.  Check with 
>  a voltmeter for 12v present at all times.
>  

As opposed to wall power?:)  I have yet to hook up my voltmeter, that's the
next step.

>  Data is the feed to the little window in the dash which shows the 
>  radio station.  Clock is a poser....I don't know, unless power for 
>  the clock loops through here, which I doubt. 
>  

Actually, most serial bus architectures have a "clock" signal which pulses to
tell you when to read each bit off the "data" line.. since clock and data
always come in pairs here, I think that's what it is.

>  > What is Com?  
>  
>  Ground or Earth, as the Brits have it.
>   

Weird.  They labeled every other ground with the standard symbol.  

>  > Any help is appreciated.  I've got a brand-new Sony XRC-900 begging to
be
>  > installed.
>  
>  The good news with this is to concentrate only on finding the leads 
>  you NEED in the existing system:
>  

This is an excellent point.  If I don't know what it is, and it doesn't match
anything on the new head unit, then by definition I don't need it.

>  *Power (Audis have no switched power - all are unswitched.)

I think this is untrue for the 96 A4Q, since many of the pins have a little
diagram with a plus sign and an open switch - I labeled these "Switched
power" on my diagrams.

>  *Antenna (amplifier) relay must be connected, even tho you have no 
>  power antenna - it powers up the Audi antenna amps.

Ah, I would never have known that.  Thanks.

>  Make sure not to leave any hot leads un-insulated!
>  

I'm actually going to make my own wiring harness to plug into Audi's molex
connectors - I discovered that Radio Shack's crimp-your-own-DB25 kit works
very well for this.  So there will be no bare wiring.

Jay