Re: 49 Packard polarity change

Posted by HH56 On 2015/7/21 16:20:16

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.