coil for 59ab with a crab distributor 6V pos.

[Planojc]

Originally Posted by tubman

There are several misleading statements in the above. First of all, almost all coils are not polarity sensitive. The primary terminals are marked positive (+) and negative (-). They work fine if hooked up correctly. The only coils that are polarity sensitive are the ones with only one external terminal. The only one I can think of now is the coil for a Ford helmet distributor. I''m sure there may be others, but they're not common or germane here.

Second, I have found that the capacitance of a condenser makes little difference in general use. If you chose really bad on capacitance, it shows up as accelerated point wear. Most modern condensers are in the low .20's microfarad range and work fine in almost all cases. If you are experiencing unusual point wear, you can improve it by increasing or decreasing the capacitance of the condenser. Depending on which side of the points the buildup occurs determines which way to go. I saw it once in an old Motors's manual, but don't remember what it is. It is very uncommon.

As to what coil to use? You want about 4 amps going through the points; anything less than than will produce a weak spark, while more is hard on points. We have all heard of Ohm's Law : I=V/R (Current - amps=Volts/Resistance). For a 12 volt system, that means a coil with 3 ohms resistance 4=12/3, while a 6 volt system means a 1.5 ohm coil (4=6/1.5). These are just general rules that are superseded in real life with things like ballast resistors and the Ford under dash resistor, but can be used to make sure components are compatible. A multi-meter and a little basic math can go a long way.

This makes sense, 1.5 ohms for 6V and 3 ohms for 12V. Thanks for the info.