BALLAST RESISTOR........WHAT GIVES?

CFD244 said

Hi Folks

What exactly does the reduced run voltage in the resistor circuit protect? Points (old system), pick-up, control module or coil? I have seen the HEI hack, but in order to eliminate the resistor, do you need to use a different coil (GM or equivalent)? Thanks FABO.

Click to expand...

Think about vehicle voltage. Remove the primary wire supplying the coil. Connect your DVOM to read battery voltage. Crank the engine over watching what battery voltage is while cranking. You will likely see about 9V. Now hook the primary wire up and start the engine. Check the voltage at the + coil terminal. Should be 8V to 9V give or take.
This was designed in on points ignition, Kettering designed it, so the coil could output the same spark during cranking as when running. Otherwise the cranking spark would be weak making cold starts difficult.
Some manufacturers used a resistor or ballast built into the coil, and three wires to it.
The HEI self regulates.