Hello all.

Less series resistance = more current for the same voltage. Current is what makes the spark "hotter" but it will also make the windings hotter, too!

When starting, the 12v system may be down as low as 9-10 volts, so one series resistor is bypassed, returning the current to proper level. 14 volts would draw 14/10 = 140% of rated current, which in turn would produce 1.4x1.4 = 256% of rated power loss, in the form of heat.

Overheated coils are not a good thing, since they fail when you're away from home, out of money, in the most miserable weather you can imagine, at the worst time and place...

Best regards,
Jim