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Speedometer HELP PLEASE !

Started 11th October 2017 at 10:18 · Greg Souter
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Hi all

Try and stick with me as I explain this long and torrid tail. I have a 1987 XJSC US delivered car, it was imported to Australia and converted to right hand drive – the conversion was very well done – except the electrical – the wiring loom behind the dash was / is a mess – a complete entangled conglomerate of wire that could only be described as a 3 yr old with a bowl of pasta.

My solution was to find a loom from a similar car and replace entirely- I found a 10/84 wiring loom and proceeded to replace, I’ve managed to get everything working apart from the speedometer and the wipers – the wipers I am convinced are a earth issue, I am working through.

The speedometer however is a challenge, I have a car with a hall effect sensor from what I can tell – a diff mounted speed transducer, not a pulse generator from the trans – which is good , as my car is manual conversion.

I cannot get the speedometer to work , or morese any registration of any voltage low or high out of the speed transducer plug in the trunk / boot ( left hand side ) behind panel.

do these sensors need a voltage fed into them or do they generate their own voltage.

please help with any comments

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    • 12th October 2017 at 23:19 #8745
      Laurence Jones
      Keymaster

      Hi Greg

      I don’t have the answer myself, but I have asked my local Jaguar Independent Garage to see if they can help. Below is my recollection of how it was described to me.

      There is a cable, like a curly data cable, that comes from the rear axle/rear transmission and disappears into the boot area. Within the boot area there are two electronic modules, the smaller of which is the module that translates the pulse coming into it (via that cable) into a voltage. This is then taken as a wire to the dashboard and it is that voltage that gives you the speedo reading.

      This means that you’ll only get the voltage out of the electronic module in the boot when the car’s moving and it’s busy translating the pulse from the rear axle.

      A thought, do you have cruise control and does it work – the reason for this question is that the cruise control works from the same pulse translation provided by the electronic module in the boot. If cruise control works and the speedo doesn’t then it’s likely that the speedo is broken.

      Not sure if the above is of any help, but might lead you to eliminate a few things.

      Laurence

    • 17th October 2017 at 06:01 #8791
      Greg Souter
      Participant

      Thanks Laurence

      I’ll do some digging, and report back

    • 27th October 2017 at 08:45 #8959
      Laurence Jones
      Keymaster

      Hi Greg

      Have you managed to make any progress on this ?

      Laurence

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