E30 Stereo wiring

Have a question about wiring for an aftermarket stereo. I've done a bunch of research, and found what seemed like some good DIY instructions, but some of them don't match up to what I have. My car is a 1988 325i Convertible with what I've been told is premium sound.

I've removed the factory radio and unplugged the in-dash fader, and then unwrapped the wiring from the fader back to a splice, or "Y" section of the harness. I've followed the remaining wiring by hand back up behind the gauge cluster and have found that the wiring does not pull out any further, and there is no other splice, plug or other point where wires seem to be spiced together.

So far, based on the instructions I found and looking at the wiring after the point where the radio and fader wiring joins together, I've identified that the RED/GRN wire is constant power, the Violet/Gray wire is switched power from the ignition, the thickest of the three BRN/BLK wires is Ground; I've also identified that the YEL/RED wire is LF speaker POS, the BLU/RED wire is RF speaker POS, the YEL/BLK wire is LR speaker POS, and the BLU/BLK wire is RR speaker POS.

There are three additional wires going back into the dash from the "splice" point. Two are white. My assumption is that the single wire (see pic) coming from the radio opening is to the remote antenna, the other white wire that goes into the wire harness is to the amp. There is one remaining BRN/BLK wire in the wiring harness.

Do the speaker wires have a ground wire associated with them? If so, which wires are they? Is my assumption about the white wires correct, or is it just the opposite? What does that last BRN/BLK wire go to? It may be a ground wire, but then it's the only one in the whole harness.Attachment 7758

OK, discovered while re-installing the factory radio that the small white wire in the harness goes to the antenna, so that means that the larger stand-alone wire coming out of the dash opening is to the amp. Just don't know what the last BRN/BLK wire goes to, or how the speakers are grounded.

Eric

Try really hard to find a plug in solution to changing the wiring harness. Some guy down the road will thank you greatly for not screwing up the wiring harness. There are tools that release the little round pins from various plugs that might allow you to plug them into a more generic plug that you could use as an adapter for your new stereo wiring. Make yourself a diagram of the before and after to use later. Try e30tech.com for a forum all about the topic. And get a complete wiring diagram off their How to and DIY sections.

I found something on the German forum
Pin ....Anschlußbezeichnung....Kabel Grundfarbe/Streifen
1..... Lautsprecher vorne links + ..........Gelb/Weiß
2...Lautsprecher vorne rechts + .........Blau/Grün
3...Lautsprecher hinten links +..........Gelb/Schwarz
4...nicht belegt - Kann für Telefon Mute (Stummschaltung) verwendet werden...Weiß/Braun
5...Plus, Klemme R (ab Zündschloß Stufe 1)...Violett/Weiß
6...Lautsprecher hinten rechts +......Blau/Schwarz
7...nicht belegt – bei späteren Fahrzeugen I-Bus.....
8...Lautsprecher vorne links - ........Gelb/Braun
9....Dauerplus, Klemme 30...Rot/Grün
10...Tachosignal für Geschwindigkeits Abhängige Lautstärke Anpassung...Blau
11..Lautsprecher vorne rechts -...Blau/Braun
12....Lautsprecher hinten links - ...Gelb/Braun
13....Beleuchtung, Klemme 58g...Grau/Rot
14...Lautsprecher hinten rechts -...Blau/Braun
15...Masse, Klemme 31................Braun
16...Automatik-Antenne, Antennenverstärker, HiFi-Verstärker (Schaltausgang 12V )...Weiß
17...nicht belegt

Does it actually have a factory amp? On some models the - wires were common and some even connected to chassis ground. This could kill your new radio. All caution.