12v. to 6v. instrument cluster

[Tony Wheeler]

Lynn, I think you mean the ammeter IS polarity sensitive, but won't be harmed by reverse polarity. As you say the Charge/Discharge reading will simply be reversed, which is easily fixed by reversing the guage connections. I imagine this will have to be done if converting to negative earth system.

As far as I'm aware the other guages are NOT polarity sensitive because they don't need to detect current direction. In any case I imagine they'd be designed to survive reverse polarity, at least temporarily, in the interests of making them foolproof!

Interestingly Ford continued to use their 6V guages long after they introduced 12V systems, by fitting a 12V to 6V converter of some kind behind the dash. Eventually they got around to making 12V guages, which simply involves recalibrating the shunt resistor inside the guage.