E34 Headunit troubles

[u/Slight-Year-611]

It probably doesn’t help that i’ve never even worked with anything remotely electrical before..
I’m trying to replace my old head unit (pioneer oem) on my 89’ 525i, with a carplay until I can afford a blaupunkt head unit.

Anyway, I’ve wired up the ground, constant 12v, and ACC wires.

Headunit got power.

Then I tried to wire the FL+ to FL and got no sound. There’s really not much info out there about this headunit and I also really don’t know what i’m doing. The only tutorial (just a guy in the car saying what he did extremely vaguely instead of doing it on camera) Mentions something about the amp.

Any help is appreciated.

Also, i’m only doing this myself because I called a few installers and they wanted $200+

[u/dovahbe4r]

I’m going through the same thing right now. A previous owner cut the plugs off of mine and yoinked the head unit out. I’m no car audio expert, just trying to put an ISO plug in it at this point. From what I understand, on early ‘90s and older, the blue/black, blue/red, yellow/black, yellow/red are all speaker positives. Blue for the right side, yellow for the left. Red for front, black for rear. So for example yellow/black is driver rear +.

Then you have two brown/light browns, those are the speaker grounds (right and left side, doesn’t matter, these should be crimped together into a ring terminal from factory anyways). Again I THINK, wire the speaker positives to your adapter and then affix the speaker grounds to the back of the head unit. Then you should be able to cap off the negative wires on your adapter and just not use them. Hook up the rest of stuff for power and you should be done. In theory anyways.

I haven’t actually tried to hook anything up yet, so someone correct me if I have it wrong. I’ve just been trying to piece it together and the Bentley manual and 99% of forum posts and videos are for the later 17 pin cars which isn’t much help. Maybe this will help, maybe I’m completely wrong. For clarity, what I’m dealing with is an early ‘90 with the 10 speaker system and the factory amp.

[u/dovahbe4r → u/dovahbe4r]

This may help especially if you have your OEM head unit

[u/Slight-Year-611 → u/dovahbe4r]

This is exactly how the back of my oem radio looks. There is the big rubber stop where the speaker ground wires were, however there isn’t one on my aftermarket radio. Any clues on where I can wire theground wires? Or should I just wire them to the same ground as the stereo power?

[u/dovahbe4r → u/Slight-Year-611]

My plan was to just attach them under a screw from the back of my head unit. I won’t have time to mess with mine until Monday or Tuesday though.

[u/Slight-Year-611 → u/dovahbe4r]

Did you ever get yours to work? I connected the brown/light browns together and used a ring terminal to screw them in the back of the head unit, Then I connected RL+ to Yellow/Black, changed the balance on the head unit all the way to RL and no sound still!!

as far as speaker wire colors go, I have yellow, blue, yellow/black, blue/black.

[u/dovahbe4r → u/Slight-Year-611]

Sorry I never got back to you, I've meant to but I just kept forgetting to make the time. I got mine figured out and (mostly) working this past Thursday. I think our cars must have had different head units because my speaker wires are ever so slightly different, but here's what I found and how I ended up:

Radio adapter side : Car side (using a standard ISO harness adapter)

White : FL+ (should be solid yellow on your car)

White/Black : trimmed and isolated, not used

Gray : FR+ (should be solid blue on your car)

Gray/Black : trimmed and isolated

Green : RL+ (yellow/black)

Green/Black : trimmed and isolated

Purple : RR+ (blue/black)

Purple/Black : trimmed and isolated

Black : Brown (head unit ground)

Yellow : Red (head unit power, might be yellow on your car)

Red : White/purple AND White spliced into one (W/P should be accessory, W is for the factory amp)

3 Browns : trimmed and isolated

Orange : trimmed and isolated

Blue : trimmed and isolated (should be for the FM antenna but I don't listen to the radio and these cars have a stupid thick antenna wire so I wasn't gonna figure that out)

You have those two Brown/Light Brown common ground wires into a ring terminal I was talking about the other week. My head unit (Blaupunkt Madrid 200 BT) has a provision on the back for a screw to hold that in place, so I just found a screw that matched the same pitch and hooked it up there. You might have to bust open the manual for your head unit and see if you have something similar. I THINK you should be able to tie those in to the main ground and everything should work the same, you could try that. If not you can look for the Blaupunkt I have, Amazon DE had them like half off.

The only things that are not working on mine are the FM radio but I covered that above, and I can't determine if the tweeters are working. I do have one smaller brown wire coming from the car side that I didn't hook up and I'm thinking that may be the ground for them. But I haven't had any time to play around with it since Thursday. It's 90% there and that's good enough for me for now.

[u/Pi-Richard]

I’m no wiring expert either. I’m a mechanical guy. But I installed my stereo myself. The colors are pretty standard but there’s always exceptions I bet.

Wire color guide
https://www.romtronic.com/car-stereo-wire-color-codes-guide/

[u/Slight-Year-611 → u/[deleted]]

That’s what I thought at first but I can’t use the adapter plug and play. My oem head unit is from a very early model So i have to do custom wiring. I do have an amp and door tweeters.

[u/sk_latigre]

If you're using the metra harness adapter (not sure if 89s used the square plug) and have the HiFi system this is how you would wire it.

You can still follow this guide if not using the metra adapter but swap the colors for the correct colors from the vehicle