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New stereo power on problem

Discussion in 'A3/S3/Sportback (8P Chassis)' started by mjepson, Dec 22, 2006.

  1. mjepson
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    mjepson Member

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    [Dec 22, 2006]
    Got my new JVC head unit, and hooked up the iso cables, and i get power to the unit. But when i turn the ignition it doesn't turn on... I know i have power cause when i press DISP on the unit, the clock shows for 5 seconds

    Have the same head unit in my vw polo and didn't have that problem there.

    audi a3 2004...

    Any tips?
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  3. mikep
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    mikep Member

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    [Dec 23, 2006]
    I believe it's because the power to the head unit is delivered via a CAN-BUS interface, my Alpine unit had to be wired to an ignition powered circuit in order to get power to it.

    There are ways round it but they're quite expensive, or wire it to a permanant power line.
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  4. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Dec 23, 2006]
    Yes, all Audi's from about 02 onwards do not have an ignition on feed to the HU. Just permanent live. The CANBUS tesll the HU when the ignition is on/off etc. Ridiculous use of a data bus, no idea why they think this is a good idea, just makes it even more difficult to change the HU.
    Just pair up the ignition on live to the JVC to the permanent live and away you go. Or if you don't want to have to turn the HU on/off manually then you'll need to run a cable. Either from the fusebox (HU will turn off when engine off), or if you want to do it properly then from the ignition switch underneath the steering column (HU will turn off when keys are pulled out).
    Bloody pain in the arse.
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  5. mjepson
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    mjepson Member

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    [Dec 23, 2006]
    Yep called up the local dealer and they said i needed to cable it like you explained... PITA
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  6. mjepson
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    mjepson Member

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    [Dec 23, 2006]
    Does anybody know how to spot the ignition switch/cable?
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  7. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Dec 23, 2006]
    It varies from car to car, just use a 12v testing screwdriver and find the wire that stays on with the ignition on and then off when you pull the keys out. I haven't done mine yet. Either that or just pick up an ignition on feed from the fusebox, I couldn't find one that stayed on until the keys were out. It used to be the fuse for Radio S-kont, but this doesn't seem to exist with the CANBUS Audis.
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  8. mjepson
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    mjepson Member

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    [Dec 23, 2006]
    Haven't used a circuit testing screwdriver before ... wouldn't know what do do :(
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  9. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Dec 23, 2006]
    I'd leave it alone then, just splice the ignition on live to the perm live on the HU side of the wiring.
    A 12v testing screwdriver is just like a mains tester but for 12v, i.e. it lights up when you touch it to a 12v. About £3 from Halfrauds
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  10. mjepson
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    mjepson Member

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    [Dec 24, 2006]
    I got it to work by hooking RED on the HU up to the fusebox.

    The car started beeping a few times while i was fiddling with the fuse box and the steering column cover.

    Now the car won't even start, cause i think it is too drained from all the days i have had the car light on without driving it...
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