Why a Resistor?

[JayChicago]

When ...Henry's insistence on using the distributor mounted coils required coil designs that were outside the normal.....The little coils only needed 4 amps or so to do a good reliable job so Ford used a 0.8 OHM ballast to control the current..

Thank you. Finaly an explanation that makes sense to me. Using a little coil required use of an external resistor. It's that simple!

 

[TomC750]

The resistor in an early Ford does not have a fixed resistance. When cold (on start up) when current has not yet heated it up, the resistance is low, allowing more voltage to the coil as the starter's heavy current lowers the battery voltage at its terminals. As the current continues to flow through the resistor (called a thermistor; temperature variable resistor) continues, it gets hotter and its resistance increases. Hopefully the engine has started, the starter is disengaged, the battery voltage increases and the resistor is in its full resistance.

After the war, the manufacturers simplified the concept. They added an additional terminal to the starter solenoid which supplied battery voltage only during starting. This wire bypassed the (fixed) ignition resistor only during startup. This resistor was initially housed in a ceramic block on the firewall. Later it was replaced by a resistor in the wiring during the points era.

Fords always started easier in cold (sub Zero) weather in the 50s than Chryslers because they always went with running voltage. At least that is my and my buddies gas jockeys' experience back then.

And mine too! I had to pull my "50 Chrysler with my Model A doodlebug out to the road, then coast the MOPAR down the hill I lived on to get it started. The A started with snow on top of the engine!

 

[SoCalCoupe]

never mind