Re: 49 Packard polarity change

Posted by HH56 On 2015/7/15 17:10:01

Nice looking car and welcome to the forum.

Most electric fuel pumps do not like reverse polarity so that is the first place to check. If you have a glass fuel filter you can see if there is anything happening. If you are lucky the pump is the type with two separate wires marked pos and neg and you can reverse the wires making the positive lead go to the frame now. Hopefully the pump was not damaged but most pulse types are solid state so it is a good possibility it was. If there is only one wire then either the pump is polarity specific with a different pump for whichever ground the car has or polarity does not matter.

As to the polarizing with engine on, it is hard to say if any damage was done. The cutout points in the reg. between those two terminals should have been closed and in theory no damage would have occurred but the regulator could be polarity specific too. You do need to verify when the engine and key is off the cutout points open to disconnect the generator from the battery. If the generator feels very hot in relation to the rest of the engine chances are the points are stuck and it is getting voltage instead of being disconnected.

If the car was purposely converted to negative ground there are a couple of other things that might need checking. One would be the coil as it is more efficient if wired according to the cars polarity. If car is now pos ground the + side of the coil should go to the dist. Also the ammeter wires may have been reversed when the conversion was done and instead of the charging indication you got before, it was really not charging. You can verify that with everything off by turning on the headlights. If ammeter reads charge, the wires were reversed and need to reverse back. If the radio vibrator was replaced with a modern solid state replacement those are definitely polarity specific.