Originally Posted by MIL1ION
The I terminal stands for Ignition
The purpose of it to supply 12 volts to the coil during CRANKING the starter bypassing the ignition switch which has a resistance wire running from the switch to the + terminal of the coil
There should NOT be power at the I terminal when the engine is running.
You see Ford coils run with 7-9 volts not 12v
A constant 12 volts would burn the coil up
OK Now I think I understand what is going on. On a conventional POINTS type ignition system the coil needs 12v at startup and then requires 7-9 volts after the car starts to run properly. So the wire running from the ignition switch is a two part wire, one part runs to the + side of the coil with a resistor in between to provide the + side with 7-9 volts when the car is running the other comes off of the I terminal and is a direct wire to the + side of the coil providing 12 volts while the engine is cranking only.
Two things though. One... I have a 12 v HEI ignition system with a coil that is a breakerless 12v coil which I assume needs 12 v all the time. The way my I terminal is hooked up is this way. It has a KEYED 12 volt wire running to the I terminal from the ignition switch which is hot when the car is in the run position. Also attached to this I terminal is a white wire that runs directly to the + side of the 12 v coil. Also, the I terminal has a red wire marked 12v running to the electric fan.. so I am assuming that whoever had this car before is using the I terminal as a mating point for the + side of the coil and as a point for the electric fan to draw its power from. The hot wire from the ignition switch is feeding power to both of these wires ONLY when the ignition switch is in the run position. When the ignition switch is in the start position(cranking) then the hot wire from the run position is dead and power is being feed to the coil and the fan via the charge through the "I" terminal. Damn I hope I am making sense....
Anyways if someone can verify what I just said that would be great. Either way I am thinking I can just bypass the whole "I" terminal all together and run a 12 v ignition switch wire to the + side of my 12 v coil and run my fan off of another 12 v source as well. What do you think?