Negative to Positive earth
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    Negative to Positive earth

    I have a tachometer which is negative earth. My car is positive earth. The diagram says it "is not designed" for positive earth. Is there a way to convert from negative to positive earth? Or does anyone know where I can get a reasonable positive earth tach?

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    The swap is (on a Minor at least) very simple -just flashing the dynamo and changing the battery leads. No idea how it may afect other instruments/fuel pump/heater on a rover, though (always assuming that you do have a Rover)

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    Quote Originally Posted by arsenic View Post
    The swap is (on a Minor at least) very simple -just flashing the dynamo and changing the battery leads. No idea how it may afect other instruments/fuel pump/heater on a rover, though (always assuming that you do have a Rover)
    Don't forget to swap the coil leads, will work but burns out points in no time.
    Here to help !

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    As said by Arsenic. Why not change the car to negative earth. Nothing really to do other than reversing the battery and coil leads (and the ammeter leads if you have one fitted) Any modern accessories that you might fit to the car in the future like Alternators, radios etc. will all be negative earth anyway.
    Last edited by stueeee; 12-02-2011 at 19:32. Reason: typo
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    I do have a Rover. I was hoping to keep it oroginal but it might be easier to switch it over. Thanks.

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    So I have been reading up on how to "flash" a dynamo. Does anyone have any tips from experience on how to do this correctly? It seems pretty straight forward but it's always good to hear from someone who ohas done it before. Also, I was toying with the idea of putting in an alternator instead. Is there one that fits well on the rover 6 cylinder?

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    There's several ways to "flash" i.e. polarise or set the residual magnetism on a dynamo, they all do the same thing though. Once you've reversed your battery terminals, just momentarily connect your "new" live (positive if you're going negative earth) to the field connection (that's the small Lucar terminal if it's Lucas ) of the dynamo. Have the field connect wire which goes back to the regulator off the field connection when you do this.

    You'll see a small spark, but you won't damage anything. When you run the car the dynamo should start charging.

    If you want to change to an alternator, any of the Lucas ACR series should line up quite well with your Lucas Dynamo front mount. You'll need to do something for the rear mount as alternators are shorter than dynamos.
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    Thanks for that stueee.

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