"Dan Thompson" wrote in message m...
I've had mag troubles
away from my home field a couple times, and it's always been easily and
quickly fixed. One time, it was that the points were burned after the
capacitor wire had severed, and new points and a capacitor were all that
were needed and on hand at the shop. A one hour delay.

It failed because the capacitor wire broke, not because the
points burned. There's a widespread misconception that the capacitor's
only job is to prevent arcing at the points, but the mag will not
spark at all if the capacitor is removed from the circuit.
The capacitor's job is to intensify the secondary coil's output by
speeding up the collapse of the magnetic field, and it does this by
absorbing the bit of current that would otherwise arc across the
points. Such arcing not only burns those points but also represents
continuing current flow in the primary, just when we want an abrupt
arresting of that flow to collapse the field. The capacitor absorbs
current just long enough that the points can open far enough to
prevent arcing after the capacitor is full.
Of all the concepts that I teach in aircraft systems, the
magneto is the one that students have the most difficulty
understanding.

Dan