Ballast resistors do nothing more than supply the coil with a dropped down voltage of 9 volts during 'run mode'.
During 'crank mode' it by passes this resistor and supplies the coil with the full 12+ volts.
Sorry will.. you flunked electronics 101
A ford ballast resistor like use dont he front mount ignitions is generally a resistive element with a thermal coeficient... the warmer the element gets.. the more resistance it is.
It's common to see resistors start at .5 ohm and climb to say.. 1.8 ohms.. etc.
The way this works, is when the resistor is cold.. it's resistance is low.. and current is not dropped much..thus during cranking, nearly max current to the coil... ater not much time.. perhaps a minute or less, the resistor heas up and it's resistance goes up, dropping current.
your example of no resistor during start is what yo would have if you used a 4 terminal ignition bypass style solenoid.
that solenoid is not used on a ford NAA.. in fact.. ford naa's were 6v and had a 6v coil and used no ballast resistor. with that ford naa on 12v, you can use a fixed resistive element in addition to the oem 6v coil, or you can switch to a straight native 12v coil and no resistors.
in many of the ford communities, the napa IC14SB is the native 12v coil of choice. it's about 16$ and robust. Nearly all my sidemount 12v tractors are running this coil.
soundguy
