I have had several friends tell me over the years that they no longer need to use the “I” terminal on their starter solenoid as they have switched to a electronic ignition. My answer is always the same. Hook it up, here’s why.

A little history. When automobiles switched over to 12 volts the ignitions still operated on 6V so a resistor was installed between the ignition switch and the coil to reduce the voltage to 6 volt ( all voltage’s given are only generalizations as the actual voltages vary by several volts). 12V would provide a much better spark for starting, and manufacturers wanted to take advantage of this. The solution was to add a “I” (ignition) terminal to the starter solenoid. When cranking 12V flows thru the “I” terminal directly to the coil, once the engine starts and the switch is released the “I” terminal is no longer energized and the coil is supplied with 6V.

So why use the “I” terminal on a electronic ignition that is already supplied with 12V from the key switch? Have you ever had or seen an engine that cranks for awhile without starting and just as you are about to give up and release the key, it starts? Having the “I” terminal connected may cure this. Most electronic ignitions take about 7-8 volts to work, there are several ways an engine that still cranks can fail to supply this voltage. While cranking it is not uncommon for even a good battery to fall below 10 Volts. This voltage has to flow thru all the wiring and connections to the key switch, thru the switch contacts and then thru all the wiring and connections to the coil. The longer the wiring and the more connections in the circuit the more the voltage will drop. Add to this, when you turned the key on, all accessories that key supplied with power, gauges, radio etc also put a drain on the circuit. How much voltage actually reaches the ignition system 8 maybe 9 volts? Also some ignition switches do not make contact with the Ignition circuit and the start circuit at the same time, or they wear to the point that they don’t, then you have no power to the ignition till you release the key.

Hooking up the “I” terminal eliminates of greatly reduces these problems. Now while cranking power flows thru a very large battery cable to the starter solenoid, then thru a fairly short wire directly to the ignition. This provides a reliable source of voltage (and don’t forget the key is also providing voltage) often curing hard starting due to low batteries, poor wiring and worn ignition switches.

Hope this helps with your next project.