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rotorwrench · 11-26-2019, 12:06 PM

The ballast resistor is more for current control than dropping the voltage even though it does both (basic OHM's Law). The coil doesn't need to draw as many amps with the higher voltage. Some coils are designed with higher primary coil resistance so that they can be run direct off 12-volt but there are still plenty of 1.5 ohm primary coils out there. The 3.0 ohm primary coil is more for a 12-volt system.

11-26-2019, 12:06 PM	#2
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,440	Re: 12 volt coil with resistor The ballast resistor is more for current control than dropping the voltage even though it does both (basic OHM's Law). The coil doesn't need to draw as many amps with the higher voltage. Some coils are designed with higher primary coil resistance so that they can be run direct off 12-volt but there are still plenty of 1.5 ohm primary coils out there. The 3.0 ohm primary coil is more for a 12-volt system.