You've pretty much nailed it. The S terminal runs to the S or Start terminal on your ignition switch. When you turn the key to the start position, it puts current to that post and makes the solenoid kick ( pass the current to the starter thru the fat cables.

The I goes to the plus side of your coil. So does another wire that comes from the I or Ignition post on the ignition switch. The one from the solenoid puts pure 12 volts into the coil to assist you in getting the engine started easily. Then when you release the key to the run position, you are now getting your current to run the coil from the ignition switch. That one usually goes through a resistor or a resistor wire to drop it down to maybe 6 or 7 volts so you don't burn up the coil while you are running.

If you haven't already done it, I would suggest one of the many wiring kits like Painless or Ron Francis, especially if you are wiring the entire truck. It is a formidable job, even for those people who have done a few. These kits make it so much easier.

One of our smarter-than-me-computerwise-members will probably post a diagram for you to look at. (how do they do that??? ) But if you have any questions, just repost.


Good luck,

Don


PS. Wecome to the forum. We need more Ford guys. Those Chevy guys push us around alot. lol