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Thread: Speedo signal blue/red wire - how does it work ?

  
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    Speedo signal blue/red wire - how does it work ?

    Can anyone tell me how the speedo signal wire works ? I believe its on 'pulses' or something like that. For example anything that uses it like the radio or factory fitted satnavs, how do they know accurately what the speed is ? Is there a voltage supply on it that goes up and down with speed ?
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    Satnav's calibrate themselves to it so that when it looses GPS it can sense how fast your going and with a built in gyroscope tell if your turning to

    I guess the factoy radio's are set up to know what the speed of the cars doing and turns the volume up accordingly

    And it is just a pulse that gets faster as you go
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    So is there a way I can build something to output the speed to a digital display ?
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    It's all possible as i'm sure you could retrofit a MK2 GTE digi dash in there but I wouldn't know how
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    I was going to have a go at building my own as I'm sure the revs/fuel and temp are either resistance or voltage fed but I thought the Mk2 took it's speedo feed off a sender cable not the blue/red ?
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    Try holding both of the buttons on the MFD for a time, this will then give you your speedin KPH

    The speed sensor works with variable pulse width to give the correct speed, on later cars with cambus the windows know how fast you are going so will move up if configured to do so.

    Over 100mph sunroof will close automatically.

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    It picks up a pulse form the front N/S ABS sensor in the wheel hub.
    Tell me what you've done, not what you're going to!

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    Quote Originally Posted by robbie601
    I was going to have a go at building my own as I'm sure the revs/fuel and temp are either resistance or voltage fed but I thought the Mk2 took it's speedo feed off a sender cable not the blue/red ?
    I believe the MK3's take it from there to
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    Mine's a basic LS model 1.6 8v - don't think it has ABS !
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    Then i'm certain they take it from the speedo cable/ head
    Want a professional job done on fitting your aftermarket electrical accessories? PM me for a quote
    Electrical fault finding also taken on
    Located in N/W London HA3, and willing to travel within reason





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