Polarity........Positive or Negative ground??
What the heck is polarity and what has it got to do with the price of tea in China???? Well, to put it simply, the polarity of a vehicle(or tractor) is determined by which battery terminal(+ or -) is connected to the frame. A negative ground system(nearly all modern vehicles are negative ground)has the "-" terminal connected to the frame, while a positive ground machine has the "+" terminal connected to the frame. How does that effect which alternator you choose?....In most cases it makes sense to switch the polarity of the machine to negative ground(I'll get to how to do that later). This lessens the chance of someone "crossing polarity" (hooking something up backwards from how it should be) in the future. There are only a couple of cases where it is better to stay with positive ground. 1.Ford 9N and 2N tractors and early 8N tractors have a "front mount" distributor and coil which makes changing the polarity of the coil to negative ground a challenge (I do offer a negative ground front mount coil, but they are expensive) 2. some cars and trucks of the fifties had electrical instrumentation, and most people aren't comfortable changing gauge polarity. So, if you have a front mount coil, or electric instuments, I suggest you leave it positive ground- that's why I build positive ground units. Otherwise, I suggest you standardize your machine and convert it to negative ground. Here's what has to be changed:
- battery connections-negative terminal to frame
- Coil connections-negative side to distributor
- Ammeter-swap wires from one terminal to the other
- remeber, if your a going from 6V to 12V to add a ballast resistor in the ignition circuit
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