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Just curious,
Were their any 12 volt Packards with the I8 built out of the factory?
Were their any negative ground Packards built from the factory?

12-volt was offered as an option in the late 30s on the senior cars for export to the British Commonweath. Up thru late 1939 these cars would mostly have been Canadian-built. These cars would have been in-line 8s and possibly a few V12s. Packard postwar marine engines were available in either 6 or 12-volt versions.

12-volt negative ground was used in 1956 across the line.

As far back as 1912 and thru 1954 Packard was 6-volt positive ground as were the majority of American car makers. There were some exceptions, Dodge used 12-volt in the era of World War I, and Cadillac flirted with a dual 6/12 volt system in the early teens.

If most were positive ground years ago, what changed all manufacturers decision to switch later on?

The reason for my questions is I'd like to convert my '51 200 I8 to 12v negative ground. My wiring harness is shot and already needs to be replaced so any reason why I shouldn't convert it now?

Why convert it at all? Unless you're going to add some power-hungry accessories like AC, there is no particular advantage to 12 volts.

A/C is definitely in the cards down the road. I live on the Gulf Coast. My prior questions were geared toward the possibility of finding a 12v negative ground wiring schematic in the archives to follow while building my harness. I'll just convert my print. Just playing out options. I do way too much thinking.

The wiring necessary for 6-volt is heavier gauge and as such will carry the current necessary for 12-volt loads just fine. There is no difference between the 6 and the 12 volt wiring schematic other than that smaller gauge (higher number) wires could be used and that a ballast resistor will need to be added at the distributor. Apart from that, there is only one actual change to the schematic -- which terminal of the battery is grounded. Flip it around so the negative side is grounded, and you should be good to go.

This, of course, assumes that you have converted everything that's either polarity sensitive or voltage sensitive (no small feat).

12-volt conversions are one of the biggest points of argument among folks in the classic car hobby. Many of us, myself included, take the stand that 6-volt is more than sufficient and that 12-volt conversions are most often undertaken to mask a problem rather than fix it. That is, unless you want to add A/C, in which case more current is usually necessary than a 6-volt generator can supply. There are ways around that, for instance by changing to a 6-volt alternator and then adding a step-up transformer to put 12-volts only where those accessories require it.

But, assuming you want to convert to 12-volt, follow the factory wiring diagram and either convert the loads or put voltage reducers before each one.

Voltage sensitive loads:
-Light bulbs (change each bulb to the corresponding 12-volt equivalent, WAGNER has a cool chart)
-Horns (horns are a very high amp draw, suggest replacing)
-Radio
-Antenna (if electrically operated)
-Starter (have it checked, may or may not be necessary)
-Heater blower motor
-Ignition system (use a ballast resistor to drop the voltage to 6v)
-Gauges (51-54 gauges operate at an average voltage of 5v; Ford used a similar setup until the 1990's, so there are several Ford gauge voltage regulators made for their 12v cars which would work to drop the voltage to the 5v the gauges like to see)

Polarity-sensitive loads:
-Heater blower motor
-Radio (if a solid state vibrator is installed)

Quote:

You can type "automotive positive ground vs negative ground" into one of the search engines, e.g., Google and get volumes of information on the subject (some of which might actually be accurate).

Thx for the info. I will continue to research. Right now just trying to get it running with the 6v system.

this is what i heard on - v +,

is that they thought electons went + to -, but found out it was - to +,,,

and they went - ground for better battery life,,, it was something like that