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JSeery · 07-31-2017, 06:21 PM

What you are looking for is ~ 3.5A through the points. This is calculated by using Current (A) = Voltage (V) divided by the Resistance (R) in the circuit (A = V/R). If the Coil is 1.0 ohm for an example and the ballast resister is 1.4 ohm the total resistance would be 2.4 ohms. Battery voltage should be ~6.4V, it will be less when cranking the engine and higher when being charged by the generator, ~7V.

If you used a 1.0 ohm ballast resistor the current would be A = 6.4/2.0 or 3.2A and running with the generator charging A = 7.0/2.0 or 3.5A.

These are just example numbers the higher the system current the hotter the spark but the quicker the points burn and the capacitors go. Like everything it is a compromise, 3.5 to 4.0A is a good range to shoot for.

You can measure the coil to see what the resistance is.

07-31-2017, 06:21 PM	#3
JSeery Member Emeritus Join Date: Nov 2012 Location: Wichita KS Posts: 16,132	Re: ignition resistors What you are looking for is ~ 3.5A through the points. This is calculated by using Current (A) = Voltage (V) divided by the Resistance (R) in the circuit (A = V/R). If the Coil is 1.0 ohm for an example and the ballast resister is 1.4 ohm the total resistance would be 2.4 ohms. Battery voltage should be ~6.4V, it will be less when cranking the engine and higher when being charged by the generator, ~7V. If you used a 1.0 ohm ballast resistor the current would be A = 6.4/2.0 or 3.2A and running with the generator charging A = 7.0/2.0 or 3.5A. These are just example numbers the higher the system current the hotter the spark but the quicker the points burn and the capacitors go. Like everything it is a compromise, 3.5 to 4.0A is a good range to shoot for. You can measure the coil to see what the resistance is.