A question on Current Voltage regulators.

I can't see why one of these control units would be polarity sensitive - they're purely mechanical.

Holden sell them, and make no mention of polarity.

I suppose it's possible the very latest versions used diodes to extend contact life, but these should be visible if you look inside. Turning them round would be the only modification needed.

It would, of course, be possible to make a truly electronic control unit for a dynamo as they do for alternators. But I've not heard of a commercial version.

I unfortunately cannot remember the exact procedure to do this , hopefully someone can remember. The only thing that determines the polarity of these units is the residual magnetism held in the solenoids inside the units. In order to reverse the polarity , it is neccesary to power one of the pins on the unit up to the desired polarity which will remagnetise the solenoid core in the desired direction , unfortunately I cannot remember exactly how (I did this several times many years ago) Regards Mike

I've altered many dynamo equipped cars from positive to negative earth, and never had a problem with the regulator. Surely any residual magnetism in a solenoid would be tiny - otherwise it wouldn't release?

I think you might be mixing it up with the (quite easy) procedure for changing the whole car from positive to negative earth by reversing the dynamo field polarity (and also reversing the battery connections of course).