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rotorwrench · 09-22-2012, 10:58 AM

The coil primary winding is wound internally in a similar fashion as a normal wire wound resistor is. They don't add a resistor inside of the modern coils, they just wind more wire into it to give it a higher resistance value internally. Round can type coils that are normally for 6-volt service don't need any extra windings. One that is designed for 12-volt service generaly is wound to work without an external ballast. The early 12-volt systems used a 6-volt coil and a ballast resistor to control the currnt going in there. The 12-volt service type coils didn't show up until after electronic ignitions became the norm.

09-22-2012, 10:58 AM	#9
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,425	Re: 6 Volt Coil Resistance The coil primary winding is wound internally in a similar fashion as a normal wire wound resistor is. They don't add a resistor inside of the modern coils, they just wind more wire into it to give it a higher resistance value internally. Round can type coils that are normally for 6-volt service don't need any extra windings. One that is designed for 12-volt service generaly is wound to work without an external ballast. The early 12-volt systems used a 6-volt coil and a ballast resistor to control the currnt going in there. The 12-volt service type coils didn't show up until after electronic ignitions became the norm.