Re: 41 Packard coil confusion

Posted by HH56 On 2019/2/5 10:49:53

Most coils are actually 6-8v. When a coil is operated at 12v there is either an external ballast resistor added or, some 12v rated coils have an internal resistor. In some more modern cars the resistance is taken care of by the wire feeding the coil supply voltage from the ign sw being a specific length of special wire which has a calculated resistance over the length. If your car has the original coil and none of those additions then while you would have a very hot spark running it at 12v, it would result in excess heat at the coil and a much shorter life for both the coil and points.

As to not switching the polarity, the coil will work either way but the spark is strongest and most efficient when it jumps from the small and hotter center electrode of the plug to the cooler outer shell. With incorrect coil polarity it tries to do the opposite but if the plugs are in good condition can get away with it. On a marginal engine or plug the spark has to work that much harder which can result ln a weak or inconsistent spark and misfires at the plug and hard to start engines. If the coil is producing a hotter spark running on 12v that deficiency would not be seen.