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Head unit compatibility

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by Nutkin, Aug 29, 2009.

  1. Nutkin
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    Nutkin Member

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    [Aug 29, 2009]
    Right my A4 has the concert system with a disk changer etc in the glovebox. i removed it today just to see if i can fit a new single din, i whacked the two plugs into my JVC units lead and it wouldnt power up!!!


    Do i need an adapter or something?

    The unit was working after i crashed my car but it did fly out in the accident.
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  3. Woorlord
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    Woorlord shifting to Hyperspace... . VCDS Map User

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    [Aug 30, 2009]
    There is no switched ignition +12v supplied to the Audi head units. ON/Off with ignition is controlled over the CAN-BUS signals.

    Adaptors do not work - you will have to source a switched supply from the fuse box - not hard to do.

    Also be aware of this problem with diagnostics with an aftermarket radio
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  4. Nutkin
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    Nutkin Member

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    [Sep 8, 2009]
    so wait what should i do. I understand they do something funny with this k line, what can i do to stop it?

    When you say sorce a switch supply you mean a piggy back fuse?


    What sort of adapter is best to use for this?
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  5. Woorlord
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    Woorlord shifting to Hyperspace... . VCDS Map User

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    [Sep 8, 2009]
    Make sure the K-line from the car side of the wiring loom is NOT connected to the "new" headunit as this can blow any "unprotected" diagnostic system that get's plugged into the car. The latest VAG-COM cables from ROSS_TECH are electrically protected, older ones and Ebay ones are not and blow the driver circuits in the diagnostic plug adapter.

    "Switched supply" means, provide a "new" wire which goes to +12v when the ignition is switched on and reverts to open circuit when the ignition is switched off. This is most easily sourced from the existing car fuse box - if you are clever you can utilise a spare fuse slot and provide a dedicated fuse supply for this feed.

    Adapter choice - you may have to find one that is close to what's required and cut/add the respective wires. Perhaps other members could enlighten us on adaptors they may have utilised?
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