starter solenoid terminals?

[travmarks]

I'm rewiring my 68 F250 240 and have a question about the ignition wiring and starter solenoid. Looking at the diagrams I understand that the small S terminal on the solenoid receives power form the ignition switch in the start position to activate the relay and power the starter motor. What I don't get is the small I terminal. Why is this needed? I see it is connected to the ignition terminal of the ingition switch and also the + coil wire....but why? Couldn't I just connect the ingition coil + to the ignition position on the starter switch with an inline ignition resistor and leave out the I terminal on the solenoid?
Thank You!

[70_F100]

Because of the way the starter relay works, the "I" terminal gets 12V when the relay is energized.

This provides a full 12V to the ignition during cranking. Once the key is released, the resistor wire provides lower voltage while the engine is running.

The ignition coil is not designed for full voltage all of the time, but the 12V during cranking provides a hotter spark.

[travmarks]

70_F100 thanks for the quick response...this makes good sense now. full 12v during startup, then the resistance ignition voltage while running. so if I do upgrade to a points eliminator and hotter coil designed to run with full 12v I will eliminate both the ignition resistance and the wire to the I terminal and just give the coil full 12v from the switch in the start and run position.

[Hawkrod]

You probably don't want to eliminate the wire to the I terminal as voltage draw will reduce voltage at the coil while cranking even if you have it wired without a resisitor. That is the reaon the voltage is tapped where it is for the ignition bypass. They could have just as easily hooked a wire to the ignition swithc to provide 12V while cranking but it doesn't work as well. Hawkrod