ballast resistor in electronic ignition cars

67Dart273 said
I've always thought it was reverse logic, that is for starting. That is, runs low during running, so you can boost it back up during cranking and compensate for the battery sagging

Yes. In fact I've seen spec that a battery drawn down to 10 Volts during starting is basically OK.

69DodgeMan said
The ballast still functions to reduce the current through the coil, which allows it to run cooler and prolongs its life.

Btw, the START feed is the full voltage and the RUN feed is the reduced voltage, and yes, the points would last longer with this setup.

And Chrysler used a ballast resistor placed so it would run a little cooler at highway speeds. At least that was the threory.
page 5 Ignition System Analysis (Session 259) from the Master Technician's Service Conference

str12-340 said
As a part of the installation directions, they had me bypass my ballast resistor. On my 340 Dart with an MSD 6AL box (old school), and billet distributor, the ballast resistor is also bypassed.

Both of these systems, along with GM's HEI, incorporate a current limiting control internally in the box.

The MSD is a little different than the others because the coil is sent power in a large pulse.