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Aftermarket HeadUnit

Discussion in 'In-Car Entertainment' started by yoda, Sep 1, 2005.

  1. yoda
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    yoda New Member

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    [Sep 1, 2005]
    Just got a few questions.

    I have just bought a new headunit for my 2004 A3 2.0Tdi Sport after my last one gave up the ghost.

    On the OEM headunit there are 3 ISO type plugs, 2 of them go straight into the new wiring harness of the headunit, but

    1. When I remove the key from the ignition the headunit stays on, the Audi one switches off. Do I need to find a switched ignition supply and if so where and what colour of wire should I be looking for.

    2. The dimmer function doesn't work, again I guess I need to find a wire that the headunit can use for this, so where to look and what colour of wire should I be looking for.

    3. The rear speakers don't work. I guess from reading other posts that this is due to Audi using an amp to power the rear speakers. So should I re-wire the rear speakers or find the wire for the rear speakers on the 3rd ISO type plug? If I re-wire how to I get at the rear speakers ? If I use the exisiting wires what are the colours for them.

    Any help most appreciated

    Scott
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  3. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Sep 1, 2005]
    Audi don't use an ignition switched live to turn the HU on/off with the keys, they use the CAN-BUS (a data bus which most aftermarket HU's aren't compatible with).
    In theory your new HU shouldn't even power up as it will only be getting the perm live feed from the Audi loom. So for it to work as it does you must have both feeds to the HU connected to perm live. Does the Sony have a wire for switched live? If so then you need to run a new cable from the fuse box to give you this feed. I couldn't find a switched live on my A4 Avant 02 model, it is usually denoted by Radio (S-Kont) on the fusebox if you have one.
    2. The dimmer is on the black power ISO next to the ground lead (looks like a little sun on the wiring diagram). This is probably not wired to anything on the Sony, so you'd need to use a piggyback onto the Audi loom and connect it to the display dimmer on the Sony.
    3. Two options:
    Either buy the interface harness and wire this to the rear pre-outs on the Sony, this will give you rears and sub.
    Or wire up the rears directly to the Sony, but you'll need to pull off the rear panels to get to the speakers and you won't get any sub.
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  4. yoda
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    yoda New Member

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    [Sep 1, 2005]
    AndyMac

    Forgot to mention I had to wire the switched cable on the HU to the perm live to get the HU working. I'm sure I had read somewhere that there's a switched live under the steering column or am I just imagining this?

    Planning to have a go at these tasks at the weekend so I'll look out for the dimmer signal and I'll let you know how I get on with the rears.

    Cheers

    Scott
    [ QUOTE ]
    Audi don't use an ignition switched live to turn the HU on/off with the keys, they use the CAN-BUS (a data bus which most aftermarket HU's aren't compatible with).
    In theory your new HU shouldn't even power up as it will only be getting the perm live feed from the Audi loom. So for it to work as it does you must have both feeds to the HU connected to perm live. Does the Sony have a wire for switched live? If so then you need to run a new cable from the fuse box to give you this feed. I couldn't find a switched live on my A4 Avant 02 model, it is usually denoted by Radio (S-Kont) on the fusebox if you have one.
    2. The dimmer is on the black power ISO next to the ground lead (looks like a little sun on the wiring diagram). This is probably not wired to anything on the Sony, so you'd need to use a piggyback onto the Audi loom and connect it to the display dimmer on the Sony.
    3. Two options:
    Either buy the interface harness and wire this to the rear pre-outs on the Sony, this will give you rears and sub.
    Or wire up the rears directly to the Sony, but you'll need to pull off the rear panels to get to the speakers and you won't get any sub.

    [/ QUOTE ]
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  5. moogie
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    moogie Member

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    [Sep 2, 2005]
    [ QUOTE ]
    Forgot to mention I had to wire the switched cable on the HU to the perm live to get the HU working. I'm sure I had read somewhere that there's a switched live under the steering column or am I just imagining this?


    [/ QUOTE ]

    There is a switched live "somewhere" in the steering column area. I had my aftermarket HU installed by the dealer before I took delivery of the car. After inspecting the installation, I noticed that they had connected a new wire to the ISO plug (in the switched live pin), and this wire is coming from somewhere in the steering column area.

    I am going to be doing an RNS-E retrofit within the next week or two, and I can take a look at where they got the switched live at the same time.
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  6. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Sep 3, 2005]
    Moogie, can you let me know which wire they tapped as I tried every fuse on the fusebox and none of them stay live with the keys still in.
    I know it's a little thing having to switch the HU off manually, but it is really annoying.
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  7. moogie
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    moogie Member

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    [Sep 3, 2005]
    [ QUOTE ]
    Moogie, can you let me know which wire they tapped as I tried every fuse on the fusebox and none of them stay live with the keys still in.
    I know it's a little thing having to switch the HU off manually, but it is really annoying.

    [/ QUOTE ]

    What do you mean with "the keys still in"? If you are trying to find a wire which stays live until you actually pull the keys out I don't think one exists. The Audi HU's get this info from the can-bus (afaik). My aftermarket HU switches off as soon as ignition is switched off with the key, even before the key is physically out of the lock.

    Anyway, I tried to take a look at where the dealer had tapped the switched feed from, but I unfortunately failed there - I got as far as seeing that the wire went inside the fuse box, but I couldn't get the back of the fuse box open to actually see where it was tapped. I may try again later if someone has any ideas on how to get the back out..
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  8. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Sep 3, 2005]
    That's OK there are plenty of fuses that switch off with the engine
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  9. moogie
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    moogie Member

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    [Sep 3, 2005]
    [ QUOTE ]
    That's OK there are plenty of fuses that switch off with the engine

    [/ QUOTE ]

    I'd guess so.

    And when it comes to usability, I have atleast found the current setup to be ok. I mean, how often do you leave your keys in the ignition lock, with the ignition off and still want to listen to the stereo. And if you do, why not turn the ignition on while you are at it - you don't need to start the engine if you don't want to /ubbthreads/images/graemlins/wink.gif
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  10. yoda
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    yoda New Member

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    [Sep 3, 2005]
    Okay,

    I found a switched source on the back of the fuse box that's behind the dash, on the drivers side. You need to take off the piece of trim off that has the switch for your lights attched to it (3 bolts, 1 in each bottom corner, then if you remove the fuse panel theres one there).

    If you remove the back of the fuse pane you can access all the wires, I had to unwrap the tape. The switched source that I use was for the can bus (no 6 I think), it's a black wire with a purple stripe. I just used a scotch block and ran a wire up to the headunit.

    I also managed to get a feed for the dimmer, On the panel that you have taken off there is 3 connectors, one for the vagcom, one attached to the light switch and one connected to the dimmer switch. I used this one to get my feed, looking at mine there was two blue wires then a brown then a gap, I used the blue one in the middle of these 3 for my feed.

    This works a treat, now when I turn off the ignition, my headunit powers off and folds away, and it dims when I put my lights on.

    Still now sound to the rears but I had a look behind the trim and it looks like a 7" speaker. I'm planning to remove the speaker and replace it with something else and then run additional speaker cable back to the headunit. It looks like I may have to take the back seat out to properly remove the side panel.

    Scott
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  11. jdp1962
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    jdp1962 Grumpy Old Moderator Staff Member Moderator

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    [Sep 4, 2005]
    [ QUOTE ]
    [ QUOTE ]


    What do you mean with "the keys still in"? If you are trying to find a wire which stays live until you actually pull the keys out I don't think one exists. The Audi HU's get this info from the can-bus (afaik). My aftermarket HU switches off as soon as ignition is switched off with the key, even before the key is physically out of the lock.

    [/ QUOTE ]

    Not mine. I've got an Alpine HU, & it stays on until the key is withdrawn from the lock. So, there's obviously a feed there somewhere you can use, but I've no idea which one it is, as I didn't fit it.
    #10

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