A 12 v coil will have 3 ohms to 3.5 ohms of measured resistance between the Small terminals (when not connected) a 6v coil will have more like 1.5 to 2 ohms. The variability is in the wires used (length and diameter) inside. I know of no resistors inside coils. They would produce heat and that is not desired. The resistors used on 12v coils with external resistor required are built to radiate heat. Ceramic blocks, or long wires embedded in wiring harnesses provide that heat sink. The 6v coils and the 12v coils for use with an external resistor are basically the same coil. Both will have the lower resistance. The bypass system, from the solenoid or relay, or starter switch, is designed to let the coil operate at cranking voltages between 9 and 11 volts for starting only. this gives hot spark, and keeps the resistor out of the circuit while cranking. (if the resistor was in the circuit, it would lower the voltage to around 4 volts (not reliable) as you have found out.) Jim
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