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Thread: MK7 Halo headlight range to cluster illum dimmer

  1. #11
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    BCM was replaced long ago with a CL, the correct HIGH version for the car. I believe all pins are there.

  2. #12
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    UPDATE:

    BCM does not have pin B33 so that's a dead end;

    a friend made me notice our common BCM pinout calls for the pot to be connected on pin A55. I tried this morning and the error stays so that's another dead end.

    we also found out this dimmer is installed only on NAR (USA market) cars so the wiring diagrams could be different. unfortunately I cannot access NAR schematics.

    I will try pin C19 and see what happens.

    it is really weird, I did plenty of retrofits on the car and everything worked out almost at first attempt; so far this stupid dimmer seems one of the most challenging things.
    my Golf came out of the factory with 13 ECUs. now she has 19. and counting

  3. #13
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    UPDATE:

    C19 is the correct pin, now I am getting TWO errors instead of one (see picture, forget databus error) and I shot a video while operating the dimmer.

    https://www.dropbox.com/s/h5t189ltfv...merFault02.jpg

    https://www.dropbox.com/s/3xu66ebh1r...merVideo01.mp4

    now I suspect the dimmer input should not be 5V instead of 12V.

    @DV52, can you please double check your diagrams? if it shows the output to BCM C19, where is the input to the dimmer coming from?
    my Golf came out of the factory with 13 ECUs. now she has 19. and counting

  4. #14
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    does anybody here from the USA can access the NAR version of erwin and kindly help me retrieve the diagram? I have VINs if needed.
    my Golf came out of the factory with 13 ECUs. now she has 19. and counting

  5. #15
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    so I have acquired a NAR wiring diagram, and unfortunately it's not very different from the ROW version.

    BCM C19 never shows as the input for the dimmer. at this point I am stuck.

    I am starting to think it might be something about BCM parameterization, or the hell I know.

    I might soon have to give up.
    my Golf came out of the factory with 13 ECUs. now she has 19. and counting

  6. #16
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    Quote Originally Posted by darkchina811 View Post
    @DV52, can you please double check your diagrams? if it shows the output to BCM C19, where is the input to the dimmer coming from?
    As I have said, I have very little information other than the extract below from the BCM pin-out. I've tried searching for "T73c /19" in all my WD s - but no hits.

    If you believe that 5V is needed then this can easily be generated in lots of ways

    Don

    VW Golf MkVII (MY13) - A3 8V hatch (MY17)

  7. #17
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    I tried the GFF with ODIS and I CANNOT see the dimmer value changing on the screen. this makes me believe that the dimmer is connected to the wrong pin.

    now the interesting question is, why does VCDS show the value changing?
    my Golf came out of the factory with 13 ECUs. now she has 19. and counting

  8. #18
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    together with the help of a friend, we finally found the solution. he has a little test set that simulates a car network with some modules, including a BCM of course.

    so we put my old MID BCM into the jig and did some testing. it's way easier on a bench than in the car.

    BCM pin A55 is a 5V reference output, needs to be wired to pin 4, input of the dimmer.
    pin 5 of the dimmer (wiper) is the regulated signal that feeds back into the BCM pin C19.
    dimmer pin 3 is ground.

    it works fine and the errors all cleared.

    now, fun fact, it turns out I also have a bad dimmer. at some point I wanted to double check the internal wiring and I opened it. it was tricky and I remember accidentally bending the wiper.

    so I'll buy another and replace it, but it will have to wait until December because I am flying on saturday.

    I wonder why this wiring is not documented on any diagram, even on the NAR version, which is the only market that actually has the option.
    I wish there was a way to tell VAG headquarters they have some wrong diagrams.
    my Golf came out of the factory with 13 ECUs. now she has 19. and counting

  9. Likes DV52, Uwe, jyoung8607 liked this post

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