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Thread: Engine START switch

  1. #1
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    Engine START switch

    https://www.dropbox.com/s/lf7uc8w0941f5wl/WD0001.pdf

    INTRO NOTE: THIS IS NOT ABOUT KESSY, I DON'T HAVE KESSY NOR I WANT IT, BY ANY MEANS.

    I would like to start my engine with a button. I mean, turn the key to ACC, one more click to IGN, but then the START phase would be a simple button, that sends the command to the starter. then I am fine in switching off the engine with the key, like I always do.

    I have attached the wiring diagram, D is the Ignition/Starter Switch and J527 is the Steering Column ECU. ideally, my plan would be:

    1) CUT the wire which is Terminal 50, so T6I/pin1. this would prevent the key from starting the engine;
    2) TAP Terminal 15 on T6I/pin5 (or pin6, gotta check with multimeter), and wire it to one side of a simple button;
    3) connect the other side of the button to the wire I cut on step 1), of course on J527 side, so T8af/pin1. this would make the button start the engine.

    up to here it all works, at least in theory. the problem is that after the engine is started the button needs to be disabled, because it would fire the starter with the engine running. not cool. not that I would go there and press it intentionally, but better safe than sorry.

    I did something similar to a Renault Clio more than 10 years ago and I figured it out, but I can't remember how. I think it involved a relay, that somehow uses Terminal 50 to disable the button.

    I also have the feeling the Golf has much more electronics involved so any comment or hint would be appreciated.

  2. #2
    Benevolent Dictator Uwe's Avatar
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    Quote Originally Posted by darkchina811 View Post
    up to here it all works, at least in theory. the problem is that after the engine is started the button needs to be disabled, because it would fire the starter with the engine running. not cool. not that I would go there and press it intentionally, but better safe than sorry.
    How is that any different than turning the key to the start position again after the engine is running?

    -Uwe-
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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    no different, except that you can't because the lock is designed to prevent that. try: once you started the engine the key doesn't turn clockwise anymore. you need to switch off the engine one turn CCW, then it will let you start again.

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    Benevolent Dictator Uwe's Avatar
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    Quote Originally Posted by darkchina811 View Post
    no different, except that you can't because the lock is designed to prevent that. try: once you started the engine the key doesn't turn clockwise anymore. you need to switch off the engine one turn CCW, then it will let you start again.
    Good point. I have a vague recollection of some older (probably non-VAG) cars that would allow this via the ignition switch. The resulting noises did not sound very pleasant.

    What's not clear from the wiring diagram is how the "Terminal 50" gets out of J527 and gets to the starter relay/solenoid. If it goes through the logic of, say J519, that module may be smart enough not to engage the starter when the engine is already running?

    -Uwe-
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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  6. #5
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    Quote Originally Posted by Uwe
    What's not clear from the wiring diagram is how the "Terminal 50" gets out of J527 and gets to the starter relay/solenoid. If it goes through the logic of, say J519, that module may be smart enough not to engage the starter when the engine is already running?
    you have a good point as well. if I am not mistaken the starter relay is actually driven by J623, Engine Control Unit. I gotta dig this a bit more, but it's probably easier to forget it. it's too much fuss just for a fancy gimmick.

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