The Ford Barn - View Single Post

JSeery · 11-12-2015, 08:56 PM

Current = Voltage / Resistance. So, if you want a max. of around 4 amps, That would be 4A = 7V / 1.75Ohms. So the resistance needs to be in the 1.5 to 1.75 Ohm range. I believe that 1.5 ohms is want is normally wanted in the system. This needs to be divided between the coil and the ballast resistor. If the coil checks ~1.5 ohms then you wouldn't use a ballast resistor. If it is more than the 1.5 - 1.75 ohm range then the coil has to much resistance for a 6-7 volt system. If it is less, then it needs a ballast resistor to make up the difference.

11-12-2015, 08:56 PM	#13
JSeery Member Emeritus Join Date: Nov 2012 Location: Wichita KS Posts: 16,132	Re: A very perplexing problem. Current = Voltage / Resistance. So, if you want a max. of around 4 amps, That would be 4A = 7V / 1.75Ohms. So the resistance needs to be in the 1.5 to 1.75 Ohm range. I believe that 1.5 ohms is want is normally wanted in the system. This needs to be divided between the coil and the ballast resistor. If the coil checks ~1.5 ohms then you wouldn't use a ballast resistor. If it is more than the 1.5 - 1.75 ohm range then the coil has to much resistance for a 6-7 volt system. If it is less, then it needs a ballast resistor to make up the difference.