Techtip13

SAVVA TECHNICAL TIP NO. 13

Changing Polarity of Batteries

I recently had the task of fitting a radio to a 1958 Singer Gazelle, which over the years
never had a radio fitted. I scratched around the store and found the perfect radio –
a late ‘60s job that worked reasonably well.

Whilst fitting it in the dash, something in the recesses of my mind reminded me of a similar
car I once owned, a Sunbeam Rapier and the problem I had fitting a radio to it –
then it struck me – these ‘50 and ‘60s English cars invariably had positive to earth battery
connections. Connect a transistor radio to it and you’ll very quickly have an “ex-radio”.
There were some radios in the early ‘60s that had a change over switch for this purpose,
but the circuitry was rather antiquated and also they are not that easy to find.

The answer is to change the battery polarity over to the modern standard of negative to earth.
This is basically a very simple operation and for those who would like to do it themselves,
the following is a suggestion of how to go about it – if, however, you are not electrically inclined,
may we suggest you ask your local auto-electrician for assistance.

·    Remove the fan belt.

·    Turn the battery around and reconnect it so the negative lead now goes to the body or
    engine and the positive lead to the starter motor.

·    Taking a piece of wire from the positive terminal of the battery, flash it on the larger
    terminal on the generator a few times. The generator will turn like an electric motor.
    Alternatively, close the circuit breaker on the voltage regulator a few times to motorise the generator.
    You have now changed the polarity of the generator.

·    Replace the fan belt.

·    Swap the connections on both the ammeter and petrol gauges so they will read the correct way.

·    Done – you can now fit a modern radio or other accessories.

If the car has an electronic rev counter, this MUST be disconnected before the change over and sent in
to an instrument repair shop for conversion to negative to earth.

WARNING – The above is a very simple operation, but if you have any doubt about your ability
in doing this, we suggest you request help.

Eric McQuillian