ClassicCar

Thanks Lew & 46 HudsonPU, but I am still confused since the answers are conflicting. Geoff where are you? If in reality the 30 Essex was negative ground, it would be the first Hudson product with a negative ground system that I have ever heard of. Thanks again for the help. Cliff Minard.

In fact all Hudson and Essex were negative ground at least up until 1931. I think the positive ground came in 1934, when there was a two-stage voltage regulation. Later on when the change came to more sophistated automatic voltage regulation with three-coil regulators the points on the voltage coil were dis-similar metals to minimise arcing and enhance longevity. However, to all intents and purposes it doesn't really matter on the earlier models if you have positive or negative ground - everything works exactly the same, and contrary to popular opinion, the starter motor won't turn backwards, nor the fuel gauge try to go the wrong way! The only effect if you change polarity is that the ammeter will read in reverse. However, if you ever do change the polarity of the battery, you must re-polarise the generator, as the residual magnetism in the field coils is what starts it charging, and if it tries charging the wrong way it won't work. All you need to do is momentarily close the cut-out points manually. Here endeth the lesson!

Geoff.