resistors and voltage

Dave,

Thanks. That makes sense to me, but it was a piece I hadn't picked up before.

Michael

The ballast resistor, varies in resistance,do to heat. At low speeds, the resistor is hotter, due to longer periods of point closing (contact) the resistance is greater, resulting in lower voltage across the points.

As engine speed increases, the resistor cools, and voltage increases across the points, but the contact time is reduced.It would be quite normal to see 6-8volts at idle speeds, and 10-12 volts, at high speeds.Ya'll have a nice day, Dave.