[Bob Bidonde]

The advent of solid state electronics drove the change from a positive ground to a negative ground. The opportunity for the ground polarity switch arose with the change to 12V electrical systems in the mid 1950s. In development at that time was an alternator which used transistors and diodes dependent on a negative ground. By 1960 the 12V alternator design was mature enough for production, and it first appeared on the 1960 Valiant.


Original thinking was that a positive ground would minimize corrosion because it made the frame a positive anode instead of the car body. The anode corrodes and the thick metal frame was able to loose some of its thickness without consequences whereas the relatively thin body metal could not cope with corrosion.