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12V Switched Supply Query - AndyMac?

Discussion in 'In-Car Entertainment' started by boffin10, Dec 29, 2011.

  1. boffin10
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    boffin10 New Member

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    Andy, the car's an A4 Cabriolet B6, 2004 reg. (non-Bose).

    A few years back you described the installation of a relay to provide the switched 12v supply for an aftermarket HU. I really like the solution & made up the relay on a piece of veraboard in a 'project box' ready to wire in. I then went looking in the car for what you described as the 'very tiny red wire' running in the plastic trunking to the left of the steering column. Undid the trunking & amongst the looms found one thick red(disregarded) & one medium red (about 2mm dia. including insulation). Is the medium red, the one you refer to? It's not really tiny - not as fine as the grey & blue running alongside which are <1mm.

    In case Andy doesn't see this, can anyone else who has done Andy's mod. successfully advise. I don't want to cut the wrong wire.

    Thanks for any help, B
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  2. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    Don't cut any wires yet, use a 12v testing screwdriver and stanley knife blade or sharp pin and test the wire goes live with the ignition and stays live until you pull the keys out. In the hard top B6 it was definately the skinniest wire in the loom, could be different on the cabrio.
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  3. Paul100
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    Paul100 Member

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    I believe there is no ignition switched 12v supply in the cabriolet (well not that I could find) its all controlled from the canbus.

    Get yourself one of these gizmos and it will give you all the outputs you need for an aftermarket hu.

    AUDI A3 A4 TT CAN-BUS ADAPTOR INTERFACE CAN-01 | eBay
    Last edited: Jan 2, 2012
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  4. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    It's all CANBUS in the non cabrio which is why you have t wire in a relay from the wiring off the ignition.
    CANBUS emulators don't actually provide a proper accessory feed, they give you ignition on only (doesn't stay live when you turn the ignition off), which you can easily pick up from the fusebox.
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  5. Paul100
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    Paul100 Member

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    it stayed live until you took the key out, same as with the original stereo.

    Its go to be easier than wiring a relay across the ignition switch. plus gives you outputs for dimming etc. if the stereo illumination dims
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  6. boffin10
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    boffin10 New Member

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    Thing I didn't like was its £55! Whereas relay out of Maplin & a few other bits were about a tenner. I didn't want to spend more at this stage as its only an old Woodstock DAB 52 radio I had in the garage from another car & I might not like it in the dash & may replace it later. Fixed stereo illumination is about right with my dash setting anyway.


    BTW Andy, it was the right wire & is now working correctly (stays on after engine shut down until key removed & comes on immediately key inserted again).
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  7. boffin10
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    boffin10 New Member

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    correction: comes on again after key inserted & then turned to first detent
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  8. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    Glad you got it sorted
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