A cold engine does not have 12 volts available during cranking, more like 9V with the starter load on the battery. GM designed a "12 Volt" coil to function properly and deliver a hot spark during cranking, and installed the resistor to protect the points when the charging system voltage went to 14+ volts to keep the battery charged.
Mechanical points, even with a condenser in the circuit, can't handle more than about 5 amps of current flow without burning. If a "12 volt" coil is designed to protect the points during cruise with over 14 volts available, the ignition primary current flow during cold (or very hot) starting will not be sufficient to deliver a good spark. The result is a long cranking session, and no start due to insufficient voltage at the spark plugs.
Now, before some of you armchair experts accuse me of lying, I've fixed hundreds of "normal crank/hard start" situations by installing the proper combination of coil and ballast resistor with a bypass wire to provide full battery voltage to the coil during starting. The situation was caused by somebody installing the wrong coil and eliminating that "unnecessary" resistor. This is not some theoretical pipe dream I'm having!
Jerry
Last edited by Hotrod Lincoln; 01/10/2014 12:20 AM.
