The condenser is sort of a shock absorber in the primary ignition circuit. Just as the points break, the primary voltage can spike to over 100 volts for a fraction of a second due to the magnetism in the coil cutting across both the primary and secondary windings. The voltage surge sees the unloaded condenser as a path to ground, at least temporarily, and heads there instead of trying to arc across the points. While the condenser is charging up, the points are getting further apart (more resistance) so when the condenser starts unloading itself the voltage can't make it across the point gap. The voltage runs backwards through the ignition circuit (and the battery) and charges up the ground side of the condenser. This rat race continues until the voltage spike dissipates, and it should be gone by the time the points close again. Bear in mind that a 6 cylinder engine at 2500 RPM cycles the points 125 times a SECOND! Electricity is FAST!
An open circuited condenser turns the points into a miniature arc welder and they burn out in a few miles. A shorted condenser stops the engine like turning the ignition switch off!
Jerry
