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Stock Head Unit CM5908 Wiring Questions...

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    Stock Head Unit CM5908 Wiring Questions...

    I apologize for the long post, but I just wanted to clarify everything. Questions are in RED.

    Picked this stock head unit up and am attempting to wire it up correctly. It is the Alpine unit with the infrared fader:

    The stereo was cut with plugs from one e30 and the harness w/ amp and premium speakers was taken from a different e30 that had radio plugs cut already. I'm trying to connect the harness to the plug leads on the head unit. (yes I realize its really not worth the hassle, but it was mostly free so I'm just going to do it, ok?)

    RR: Right Rear - BU/BL
    LR: Left Rear - YL/BL
    FR: Front Right -
    BU - connects to-> BU/RD
    BR - connects to->BU/BR (common ground splice)
    FL: Front Left -
    YL - connects to-> YL/RD
    BR - connects to->YL/BR (common ground splice)

    Should the Front Plugs have the Brown ground wires there or do they not go into the head unit? Do the Rear Plugs need some Brown grounds too?

    MP: Memory Power -
    YL - plugs to-> RD/GN - from power distribution
    IL: Illumination - WT - plugs to-> RD/GY - from power distribution
    PA: Power Antenna - WT
    G: Ground - BR/BL - from ground distribution
    +: Switched Power - VL/GY - from power distribution

    ??: Unknown - BL/BR - plugs to-> ??
    ??: Unknown - WT/BR - plugs to-> ??

    This plug is hardwired to the back of the head unit: What does this plug connect to?

    Thanks for any help, if anything needs clarification please let me know.

    Last edited by e30 Luv; 05-12-2009, 09:55 AM.

    Info update

    Thanks to help from an M42club member who gave me the heads up on current wiring diagrams (318is Electrical Manual Link), I figured out the extra ground wires. I haven't hooked this up yet but I'm 99% confident that I've wired this up correctly.

    Everything in my first post is correct, Except the 2 Brown wires that feed to the Front Left and Front Right radio plugs. Instead they both hook together to a BR/BK wire that is factory spliced off the BR/BK wire to the radio ground.

    Here is an image I drew up:

    The part that was throwing me off is outlined in the red dotted square. I think the harness I was using was intended to have the exterior mounted fader button, which is why the left and right channels had separate ground wires.

    I still can't figure out what the extra radio plug is for (Blue/Brown wire and a White/Brown wire going to a 2-pin plug). The diagrams I have been looking at show a "case ground" for the radio - but the wires in the diagrams are both brown and do not have a plug.


      Info update

      Wanted to add that everything works. Radio, bass/treb and bal/fade functions all work perfectly. The diagram I drew up is correct. Still don't know what the extra plug is used for - I know its not the CD Changer option because that is a round 13pin plug. Have not tested the cassette player yet.


        so how would you go about wiring an after market head unit?


          :retracted question:
          Last edited by e30Rob; 05-25-2009, 09:09 AM.
          Need Custom spacers and adapters?

          PM for information


            Originally posted by e30 Luv View Post
            ??: Unknown - BL/BR - plugs to-> ??
            ??: Unknown - WT/BR - plugs to-> ??

            This plug is hardwired to the back of the head unit: What does this plug connect to?
            I realize this is a very old thread but it was crucial during my CM5908 installation this weekend. I think I found an answer that wasn't clear as well.

            I don't think these wires hardwired into the back of the head unit are for the E30. I happen to have the original owners manuals and the installation guide references a "dot matrix" display for this harness. This same radio was also used in 5 and 7-Series so I'm guessing there was an LCD display in the instrument cluster which displayed radio information.
            1989 BMW 325is Coupe - Alpine White


              I don't know what this mystery connector does either, but here's what I do know: On the rear PCB of the radio where these two wires attach, they are labeled LAC and DAC (bottom left of pic). I probed both of these while using the radio and couldn't do anything to cause them to do anything interesting, they seem to just be pulled up to 5V always. So if it's any kind of digital communication to an external display, maybe it's only used with the CD changer?

              DAC makes me think digital audio converter, maybe some kind of DAC turn on set by the CD changer? Don't know why it wouldn't just go through the DIN connector though. Or what LAC could stand for.


                Reviving an old thread here for help.

                I would like to return the stereo system in my '88 E30 M3 to stock OEM configuration. My car was built in 12/87 and was delivered with the premium sound option (remote Blaupunkt amp in the trunk, Bose speakers, 6 CD changer in the trunk and fader/balance switch on the dash). I believe the original head unit was an Alpine CM5907.

                When I purchased the car an aftermarket head unit had been fitted, the rest of the original system remains intact and untouched. The original wiring harness in the dash has been heavily spliced into and cut for the aftermarket head install but appears to all be there.

                I have sourced a nice condition with code Alpine CM5908 head unit which I believe was installed in the e30 from 1989. I would like to install this in the M3.

                My question is; what changes/additions if any do I need to make to the original CM5907 wiring/plugs to get the CM5908 functioning correctly.

                I'm aware of the additional brown ground wire on the CM5908 front left and right speaker plugs that the CM5907 does not have, I'm not sure where this additional ground wire runs to off the speaker plugs.

                Is there any other differences additions I need to deal with?




                  This post as incredibly helpful in reverting back to my OEM radio.
                  I have started entailing the web.
                  Attached Files


                    I BUY/SELL REFURBISHED CM5907s & CM5908s

                    DB vert plastic bumpers
                    OEM Keys
                    MTech1 docs

                    88 ix Lach/Card
                    91 ic Calypso 3.1
                    86 Cosmo 2.7

                    OEM+ or bust!

                    reelizmpro: I will always be an e30 guy.. I still do all of my own labor
                    TrentW: There's just something so right about a well-built M20 in an E30
                    e30m3s54turbo: I save my money for tuner parts.