Condensers can fail in two ways- - - - -open circuit, or shorted. A short, which is extremely rare, results in an immediate engine stop- - - - -just like the points staying closed all the time and preventing the coil from producing a spark. An open circuit, where the condenser fails to absorb some, or all of the voltage spike in the primary as the coil fires, results in a high current arc across the points every time the coil fires. The points burn, and the engine stops- - - -just not as quickly as with a short. Ideally, a "12 volt" coil with the proper size resistor in series with it will see around 7.5 to 9 volts applied to the upstream primary terminal when the resistor is in the circuit. The remainder of the charging system voltage (up to about 14.5 against a fully charged battery) will be dissipated by the resistor.
Jerry
