Radio Wiring and Amp Bypass

[6670charger]

I'm having a problem identifying what else I need to hook up for my car. I have an '88 325i convertible with what I think is premium sound (based on what PO told me), but I don't know for sure. The car does have a fader in the dash. I've stripped harness back about a foot from the fader as instructed in other threads, and found all of the wires as someone else listed below:

CD player colors ......... BMW wiring colors
Yellow (12V battery) ......... Green/Red (12V unswitched)
Red (12V ignition) ......... Purple/White (12V accessory)
Black (Ground) ......... Black/Brown (Ground)
Green (Left rear positive) ......... Yellow/Black (Left rear)
Purple (Right rear positive) ......... Blue/Black (Right rear)
White (Left front positive) ......... Yellow/Red (Left front)
Gray (Right front positive) ......... Blue/Red (Right front)
Blue/White (Amp turn on +12V)

My problem is that the speaker wires (far right colored wires in the pic) aren't in twisted pairs. The only speaker wires that exist in the harness are the colored positive ones listed above. There are two BRN/BLK wires; one goes from the factory deck to the fader, and there is one additional BRN/BLK wire that goes into the harness along with the speaker wires. I have no idea which wires, if any, are the ground wires for the speaker wires. I could strip and hook this up in minutes if I only knew how to ground the speakers.

Also, I assume the big thick WHI wire coming out of the left end of the stereo opening goes to the factory amp? I don't plan on hooking that up to anything based on what I've read so far.

[CB-M3]

^You still have all that black tape wrapped up. Did not peel far back enough. Follow the positives back for each speaker it should be in twisted pairs. I had a newer model premium and the twisted pairs were definitely there. They joined into one of the brown wires as they got closer to head unit and connector.

Yellow/red+ driver front
Yellow/brown - driver front
Yellow/black+ driver rear
Yellow/brown - driver rear
Blue/black + pass rear
Blue/brown- pass rear
Blue/red+ pass front
Blue/brown- pass front

One comment to make is Luke has all the speaker negatives as Brown/Orange on the 1st page. That may be confusing because I know on mine the negatives had their own individual striped colors. They were not all brown/orange.

[mikracer]

Will an aftermarket head unit power the factory premium speakers well? And will this wiring maintain all speakers working? I have an '88 325is with the premium stereo.

[6670charger]

An aftermarket head unit should power the factory speakers just fine. I had a few BMW's of this vintage in Germany the past couple of years. All of them had aftermarket stereos, and the stereos powered the speakers with no problems. In fact, the unit I'm installing I brought back with me. It's a JVC unit from a few years ago.

[6670charger]

^You still have all that black tape wrapped up. Did not peel far back enough. Follow the positives back for each speaker it should be in twisted pairs. I had a newer model premium and the twisted pairs were definitely there. They joined into one of the brown wires as they got closer to head unit and connector.

Yellow/red+ driver front
Yellow/brown - driver front
Yellow/black+ driver rear
Yellow/brown - driver rear
Blue/black + pass rear
Blue/brown- pass rear
Blue/red+ pass front
Blue/brown- pass front

One comment to make is Luke has all the speaker negatives as Brown/Orange on the 1st page. That may be confusing because I know on mine the negatives had their own individual striped colors. They were not all brown/orange.

I'll give that a shot, however, just looking at what's exposed through the tape as it goes back, it doesn't look like the wiring changes any for quite a ways. I hope it doesn't turn to twisted pairs way up inside the dash or I'll never get my hands in there to work on the wiring.

Also, I don't plan on disconnecting the amp at the back right now. Guess I'll have to wait and see how things sound before I decide for sure.

[mikracer]

An aftermarket head unit should power the factory speakers just fine. I had a few BMW's of this vintage in Germany the past couple of years. All of them had aftermarket stereos, and the stereos powered the speakers with no problems. In fact, the unit I'm installing I brought back with me. It's a JVC unit from a few years ago.

Thanks!

And just to clarify, does wiring this way (from post #1) bypass the amp? It says something about connecting the wires in the trunk, which leads me to believe it does, but then are you running new wires to run the front speakers? I'm a little bit confused.

[MrDomino]

I'll give that a shot, however, just looking at what's exposed through the tape as it goes back, it doesn't look like the wiring changes any for quite a ways. I hope it doesn't turn to twisted pairs way up inside the dash or I'll never get my hands in there to work on the wiring.

Also, I don't plan on disconnecting the amp at the back right now. Guess I'll have to wait and see how things sound before I decide for sure.

I didn't have the twisted pairs either and just decided to remove the amp since I couldn't get it to work with the amp. See the image I just posted a few days ago that shows how to wire up the speakers without the amp. Trust me, it'll go much smoother if you just scrap the amp. All you need to do for your situation is remove both front kickpanels and then run new wires to the headunit for the front two speakers.

[6670charger]

If you didn't have twisted pairs, how did your back speakers ground? I can see how running new wire to the front might make a ground for the front speakers, but, don't they all need to be grounded?

Sorry. I'm an electrical novice. I know the basics, and just enough about wiring to get myself into really big trouble. This is why I was hoping to get away with using the factory wiring. It's already there and run to where it's supposed to be, and is supposedly really good wire. I just need to know how to ground the speakers, as the only wires I've found for them so far are the positives. I'll unwrap some more of the harness to see what I find, but based on what I've seen so far, I have a feeling it's going to be nothing more than what I have unwrapped right now.

I'll have to say that the E34s I had in Germany were a heck of a lot easier to work with for stereo wiring. Those cars actually have a harness adapter for them that is completely plug n' play.

[MrDomino]

Yeah they all need to be grounded. You're going to take the amp out and then splice the rear speaker wires (two positives, two grounds) in the trunk to the two sets of wires that run to the front of the car already which are yellow/red, yellow/black, blue/red, and blue/black. Check out the picture I posted. It shows what color wires to connect.

It's going to be about a week but if you're willing to wait I'll eventually have pictures showing how I wired stuff up in the trunk.

[CB-M3]

just scrap the stock amp. the new head unit should have amp integrated.

[6670charger]

Yeah they all need to be grounded. You're going to take the amp out and then splice the rear speaker wires (two positives, two grounds) in the trunk to the two sets of wires that run to the front of the car already which are yellow/red, yellow/black, blue/red, and blue/black. Check out the picture I posted. It shows what color wires to connect.

It's going to be about a week but if you're willing to wait I'll eventually have pictures showing how I wired stuff up in the trunk.

OK, think I can figure that out from your pic. I'm going to check out the dash harness in a few minutes and see if it actually does have the twisted pairs or not. If not, what do I connect at the dash? Do the yellow/red, yellow/black, blue/red, and blue/black wires become grounded because I rewired in the trunk? I guess that's what I don't get for sure. If rewiring in the trunk as you did grounds the four colored dash wires so that all I have to do is connect them to the correct colored pairs of wires coming from the new deck, that should be easy enough.

[StereoInstaller1]

I'll give that a shot, however, just looking at what's exposed through the tape as it goes back, it doesn't look like the wiring changes any for quite a ways. I hope it doesn't turn to twisted pairs way up inside the dash or I'll never get my hands in there to work on the wiring.

Also, I don't plan on disconnecting the amp at the back right now. Guess I'll have to wait and see how things sound before I decide for sure.

You have a special case, I have seen this before.

The easy thing for you to do is use the stock amp.

It will sound just fine, feed it the 4 speaker positives and make sure to ground the brown/black, plus make sure both white wires are used, unless you don't care about the antenna.

[6670charger]

Well, I stripped the harness tape off of the wiring behind the deck all the way up to the gauge cluster (pic below). So far, I have single wires all that way back up as far as I can see and feel. If there are twisted pairs on this harness, they're behind the gauges, and I'm not tearing the entire dashboard apart to do this. That's just insane.

I still question whether I have twisted pairs or not. I believe I have premium sound. I have speakers and tweeters in the doors. The pic below is of the stock deck itself if that tips anyone off.

Guess my question from above still stands. If I eliminate the amp in the trunk and rewire back there as shown in MrDomino's pic, will this ground the four colored speaker wires in the dash so all I have to do is connect them to the new deck?

Thanks.

[StereoInstaller1]

Well, I stripped the harness tape off of the wiring behind the deck all the way up to the gauge cluster (pic below). So far, I have single wires all that way back up as far as I can see and feel. If there are twisted pairs on this harness, they're behind the gauges, and I'm not tearing the entire dashboard apart to do this. That's just insane.

I still question whether I have twisted pairs or not. I believe I have premium sound. I have speakers and tweeters in the doors. The pic below is of the stock deck itself if that tips anyone off.

Guess my question from above still stands. If I eliminate the amp in the trunk and rewire back there as shown in MrDomino's pic, will this ground the four colored speaker wires in the dash so all I have to do is connect them to the new deck?

Thanks.

Don't, just use the amp.

[6670charger]

You have a special case, I have seen this before.

The easy thing for you to do is use the stock amp.

It will sound just fine, feed it the 4 speaker positives and make sure to ground the brown/black, plus make sure both white wires are used, unless you don't care about the antenna.

If I understand you correctly, it sounds like I should be able to just connect the 4 speaker positives to the speaker pos/neg wires from the JVC deck. I'm not sure what you mean by grounding the brown/black wire. I have what appears to be three of them. One is thicker, and what I believe to be the main ground wire. The other runs from the deck to the fader, and the third from the fader out to the harness and runs along with the speaker wires. It may just be an extension of the fader to deck wire.

Also, I have two white wires. One is thinner and plugs directly into the radio via a tiny prong connector. The second is thicker and runs independently of any of the other wires. If memory serves, it connects inside of a thick rubber sleeve to a second white wire coming out of the deck somewhere. Are they both to the antenna? If so, do they both connect to the blue antenna wire from the JVC?

Thanks.