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Old 22nd Aug 2010, 9:53 pm   #4
murphyv310
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Join Date: Sep 2006
Location: Kilmarnock, Ayrshire, UK.
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Default Re: Old car radio - how to change polarity?

Hi
It is easy to reverse the polarity of the car. It must have a dynamo as alternators are for negative earth.
Disconnect the battery and the dynamo leads, reverse the battery leads and reconnect it then flash the "F" connection of the dynamo with 12v positive from the battery. Disconnect the earth from the battery, reconnect the dynamo and reconnect the battery, hay presto a negative earth car.
Gauges should still work ok but if it has an old electronic taco beware, do the radio instead.

As to the first post are you sure its the car with the negative earth, as most old cars are positive earth, all modern radios are Negative earth.
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