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Thread: New Sony head unit - botched wiring...

  1. #1
    Constant Bitrate SamDude's Avatar
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    Sep 2004
    London (UK)

    New Sony head unit - botched wiring...

    I've bought a Sony M8800, which falls into Phase 1 of my Carputer project (see This Thread: I'm new, I know what I want, help me! for the background).

    I've had a bit of a botch with the installation of the head unit....

    Having pulled out the factory head unit, I plugged in the ISO harness (included with the Sony) and then connected the harness to the Sony (= easy)

    It worked fine for a couple of minutes (I hadn't secured it in the DIN slot at this point, just resting on my lap).... While testing a CD, I must have tugged on the harness a little too much and I saw a spark inside the DIN slot - I'm not sure where it came from, but the new head unit went night-night.

    Since then, I tried the original Golf head unit, it powers up fine. It's asking for the 'SAFE' code. I'll have to contact VW for it, but this is not a problem.

    I've connected the new Sony head unit in my other car (Audi A4). It already has a Sony head unit, so swapping the units was easy. The new Sony works fine in the other car - so it doesn't seem to be damaged (tested the new ISO harness as well, it checks out fine).

    This narrows down the fault to the wiring loom in the Golf (unless someone tells me otherwise?).

    I retried the new Sony head unit in the Golf and nothing had changed (why would it have?...). I then swapped over the red/yellow connections to change from switched to continuous power supply. The lights still don't come on, but I can now open and close the motorised face panel.

    This means that its getting power, but something is still wrong....

    Is it shorting somewhere or maybe fuse(s)?

  2. #2
    Low Bitrate
    Join Date
    Sep 2004
    OK, so if I read correctly, the Sony HU works fine in your other car, your factory HU works fine in your car, but the Sony refuses to work (except the motorised face) in your car. Right?

    That odd, you've taken the troubleshooting steps to narrow it down and have essentially ruled everything out. It seems though that possibly the existing head unit is not using a wire that the Sony does, or that it's making a better connection with the harnass.

    First off, I know many new head units need to be "juiced up" for a few minutes, that is they have to have power supplied to them for upto 2 minutes before functioning properly. Make sure you are leaving it plugged in long enough. Second, the only wires that should matter initially are the yellow, red and ground. Get a volt meter and test yellow and ground and red and ground with the car on accessorry. See if you get readings on both. No reason why you shouldn't since your old head unit works.

    Check to see if possibly the any pin in the harness or on the back of the stereo is lose or charred from the mishap.

    Last but not least, I had a sony wiring harnass fail on me, and it turned out that one of the pins in the sony harness had gotten pushed in or too far to make contact with the deck. It was the yellow wire in my scenario. I had to get a small screw driver and push it back into the harnass and then zip tie all the wires close to harnass to keep it from popping out again.

    Hope this helps.

  3. #3
    Constant Bitrate _maelstrom's Avatar
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    Aug 2003
    Check the fuses in your Golf. It sounds like you have an exposed wire that grounded when you tugged on the wire loom and it just blew a fuse. I'm almost posetive that's all it's going to be.
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  4. #4
    Constant Bitrate CHUPACABRA's Avatar
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    Mar 2004
    G'ville S.C.
    Sounds definatly like a fuse problem!
    Eather that or a fuseable link.
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  5. #5
    Constant Bitrate SamDude's Avatar
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    Sep 2004
    London (UK)

    Thumbs up

    Fuse located (with the help of a list of fuses at, diagnosed 'broken', replaced and panic over

    Thankos muchos to all that chipped in...

    ...back on track with Phase 1 we go

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