testing for the existence of ballast resistor in my car

[JayChicago]

I have tested the output voltage of four original resistors and one aftermarket resistor. As they warmed, each dropped the voltage by only 0.2-0.4 volts. A few tenths of a volt seems to me to be negligible.

I think the theory of the higher voltage when cold to help starting is a myth. That technology did come into common use during the fifties, but then the resistor was actually by-passed during cranking. Not on our cars.