Packard Forum Index » Post-War (1946-54)

Excuse my ignorance but what is the point to changing the polarity? I had heard years ago that a positive grounded system was more prone to rusting, but have no idea if that is true.

On a stock system no reason but IMO most of the polarity changes are done accidentally or absentmindedly by an owner or even a mechanic. I guess it is not surprising that so many are changed because many younger people don't realize they used to make cars with positive ground. Most of us who were around when the cars were made that way are close to retirement or even past and the younger guys may have never seen or heard of one. I think the explanation of what will still work or not if polarity did get changed is needed as more of a reassurance that normally no damage will be done.

Answering your question, one reason to do it deliberately is in conjunction with a voltage change to 12v. Almost all of the modern accessories that people want to use and are willing to convert the voltage for require a negative ground. While there are issues lowering the voltage to a stock component at least it is reassuring to know once the voltage is taken care of everything stock will still work with a polarity change.

As the poster that started this thread found out the hard way, where it gets interesting is when you get a "new" car and don't know what or maybe why something has been done before. A modern polarity sensitive component being installed is a common one that will give grief. My cars are a good example of a few upgrades to the electrical that the next owners may encounter and wonder what was he thinking. At least mine are documented and nothing polarity sensitive (yet) but it will still raise an eyebrow or elicit a bad word or two.

Hmmm...you got me thinking...Since the engine is out of the car and since I am installing a new generator...perhaps this would be a good time to reverse the polarity of the electrical system?

The car is otherwise stock including the radio. It has an electromatic clutch and an R-9 overdrive.

So reading this thread it seems that the only items to address in reversing the polarity is the following:

1. Reversing the battery cables.

2. Reversing the two wires on the Carter electric fuel pump

3. Reversing the distributor and coil wires (can you please elaborate)

4. Ammeter wires (I cannot tell if these actually do need to be reversed).

Is that it??? It would seem that there is more to do than these minor items???

THANKS for the info!!!

Bill

Nice 22 series '49, aka a '48 '49. I prefer those, they don't have the beltline chrome spear strips like a 23 '49. The bumpers appear to be '49, but the front doesn't show. If front has center cut outs and paint, it '48, if none, it's '49. Might just be rechromed or replaced?
I don't remember seeing yellow as a factory color, but I'll check.
It really makes no difference to the electrons which way they flow. But when you want them to do work, it does.
They went to 12V and negative ground to reduce wire size and decrease voltage drop impacts. This has been covered before. With 6V, you easily run into low voltage issues; slow starting, dim lights etc, and wire heating because of the increased amperage to get the same power. Properly installed and maintained 6V is not a problem.
To the budding polarity changer, you might have generator issues, if you just change the ground. Talk to an auto electric shop first. As it adds no value, may decrease it, I'd leave it alone, make it factory correct, as it'll cause confusion to subsequent owners like the first guy. If you make changes be sure to document them to stay with the car. eg; My other car had left hand thread lugs on the left side and the former owners tire jockey right hand impact wrench "idiots" couldn't get them off without busting most of them. So I changed them to rightie when I replaced the busted studs. That "L" stamp means left hand thread, if you know what it means, otherwise you torque away. The left spindle nut is another story so I have spare nuts for that to go with the car. I never stop getting amazed what people do to autos...

Not sure I understand why you want to reverse the polarity unless it is incorrect now.

To elaborate on the coil change, the coil terminals should be marked with a + and - if it is an aftermarket or universal coil. If it is the original coil it may use the same + or - but may also say something like BAT or IGN and DIST. There may be other designations but you get the idea -- one terminal is for the hot wire and one is for the points.

To have the coil oriented properly an aftermarket coil would have the terminal designation matching the battery ground polarity going to the points since points are in the ground side. On the Packard with positive ground the + terminal on the coil would go to the distributor. On an original coil it gets more interesting if the coil is not for the car it is in. In any case you need to know which polarity the mfg used. The terminal labeled BAT or IGN would go to the non grounded polarity. If you reverse the polarity from the mfgs spec then the BAT terminal would now go to the distributor and the the other terminal receives power. Easy enough to do on a coil with both terminals exposed but those with the armored cable have a bigger job in reversing polarity. One terminal on those coils is well hidden and not easily accessible so some ingenuity and fabrication is needed to swap connections. Those coils may just be easier to leave as is -- They will still work -- just not as efficiently.

You can tell if the ammeter needs to be reversed by turning on the headlights with the engine off. If the ammeter indicates charge with the headlights on then the wires need to be reversed.

If nothing besides the pump is solid state then other than repolarizing the generator, there should be nothing else required. There is some question on what changes are in a regulator that is designated as being for a specific polarity ground. I don't know exactly what the difference is but those who swap haven't reported any dire issues.

Nice lookin ride!! I finally gave up and put a 12 v - gr battery in my 52,
got a power gen distributer that bolts right in in 3min ,a pertronix points eliminator and a hot coil they supply and presto ,no issues as was just pointed out the engine doesn't care ,the voltage regulator is no longer needed ,it'll charge at idle ,no more hot or cold start issues ,cosmetically invisable too

Assuming you mean the PowerGen replaced the generator, not the dist. If so does your red BAT idiot light still work as it did before the swap or did you have to rewire anything in the indicator circuit when you eliminated the regulator.

I think they ought to do a "real" reality TV show called "Crack Pot Garage". They could feature some of the jerks I've had to deal with.