6V Positive Ground Alternator Upgrade
How do I make my Model A Ford more usable or user friendly without damaging the originality or value?
There are some immediate items on the original car that should be upgraded to improve function and safety.
First is the generator. The Ignition, starting system, battery, and lights all depend on the generator to maintain a full charge on the battery. If the generator or charging system in your Model A ford is not doing a good job of keeping the battery charged then regular usage of those elements is questionable.
When the Model A was designed in the 1920's, the charging systems were only as good as the technology of that time. So, the charging rate (approx 15 AMPS) was all you got and the voltage regulation (automatic capability of keeping the battery charged) was not even available yet. This required the driver to constantly adjust the output of the generator so the battery was
not being over charge or undercharged . If you turned on the lights you had to adjust the generator output to support the extra load you just created with the lights. If you did not make this adjustment then you would discharge your battery. Then, when you turned the lights off you had to re-adjust the output on the generator to the non-lights condition. If you did not make this adjustment you would overcharge the battery and boil out the electrolyte in the battery. If this regular maintenance was not done your battery would eventually fail. Battery life in cars with these old generators was short due to the maintenance issue and lack of an automatic voltage regulator. In short, the charging system on a Model A Ford from the factory was very low on output and required a lot of regular adjustment.
What is a good solution?
All modern cars built today use high efficiency alternators with automatic voltage regulators. The high efficiency alternator replaced the generator in the 1960's and featured automatic voltage regulation to keep the battery charge regardless of loads. So no manual adjustment is required at all and the battery stays charged automatically. When the generators were abandoned by the auto manufactures in the 1960's and alternators became common, used alternators in junk yards, etc. became available for re fitment onto older cars and the benefits of this modern device were found to work on older cars but there was a problem. The alternators that were available were all 12v negative ground and some of the old cars including the Model A Fords were built as 6 volt positive ground. The solution was at that time to change the Model A Fords over to 12v negative ground and enjoy the modern convenience of the alternator on the old car. This 6 volt positive ground to 12 volt negative ground conversion was and still is an involved change. The original generator had to be replaced with a a suitable alternator unit, this was the easy part involving a modified mounting bracket but then the battery, ignition coil, wire grounding configuration had to be reversed (including the amp meter) to negative ground arrangement and all of the lamps had to be changed to 12 volt. Then you had the starter motor and the horn to modify to handle the increased voltage. This was a lot of work but the benefit was a modern charging system upgrade with automatic voltage regulation and much more current output but it was not an easy job.
Today the solution is much easier and less work to install. In the late 1980's NuRex designed and began producing the Nu-Rex 6 volt positive ground alternator that was specially designed for the low RPM Model A Ford. This alternator eliminated all of the additional work and cost
associated with upgrading the Model A Ford to a modern high efficiency alternator with an internal automatic voltage regulator. You now could simply remove your old Model A Ford generator and install the new Nu-Rex 6 volt Alternator and that was all you needed to do. And, it was available in 30 amp or 60 amp output configurations. A simple solution was finally found and available. The Model A parts distributors now have a real modern Nu-Rex
Alternator upgrade for sale to the hobbyists that is easy to install and no changes are required to the car or the wiring. The benefits include: longer battery life, no maintenance automatic voltage regulation, automatic ONE WIRE turn on and automatic turn off with no modification to the car or the original car wiring and an upgraded current(amps) output to support even
halogen headlights and additional accessories. And, due to the safety upgrade considerations, many Model A Ford show events accept these upgrade alternators when being judged as practical safety improvement. For these reasons many hobbyists consider the Nu-Rex 6 volt positive ground alternator a "MUST HAVE" upgrade product.