Hi, I am trying to wire a 3 post Ignition switch to ford starter solenoid. The ignition switch is labeled "batt" "IGN" and "Solenoid". Is this the correct way to wire a 3 prong ignition switch? "batt" Terminal to 12v "Ign" do I run it to the "I" terminal? "Solenoid" to the "s" terminal? Thank you
I would run batt to 12v Ign to the coil and solenoid the small S term on the terminal on the solenoid
The I terminal is used for the ballist resistor byp*** circuit for point type ignition systems. Do not connect any circuit from the ignition switch to the I terminal on the solenoid. Make sure the base of the starter solenoid is grounded or mounted to a grounded metal surface.
You need to check for continuity between the "Batt" and "Ign" when the key/switch is held in the cranking/start position. Some switches don't have power to the Ign until the key is released to run. If this ^^^ is the case, then run a wire from the "I" on the starter relay to the coil or ign circuit. [even with an HEI] The starter solenoid [on the starter motor] needs to be bridged to the main starter cable. [eg: when using a GM starter motor]
That drawing is wrong. If there is a ballast resistor there is a lead from the I post to the coil terminal that the ignition wire though the resistor connects to + or - depending on the polarity of the battery as the coil polarity always matches the battery polarity. The I post is only used if you are indeed byp***ing the resistor and it will not work properly if connected to the switch side of the resistor. On some cars and trucks it may be needed after an ignition swap because the original design of the system relies on the byp*** wire to provide power to the coil while cranking. I'm thinking that late 50's V8 chevy trucks work that way. The switch does not provide power to the coil when you are cranking. Who ever did that drawing probably intende it for a electronic ign conversion that doesn't have a resistor. Run the wire from the I post back to the switch to get power to the coil when cranking rather than running it to the coil.
^^^. The ballast resistor byp***. IIRC, mid 50’s Chevy cars did it with a lead from the starter, byp***ing the resistor. Same idea. Full 12 volts when cranking, resistor voltage when running.
The drawing is correct! you conveniently didn't mention [or read] the very first paragraph of my posting. here: You need to check for continuity between the "Batt" and "Ign" when the key/switch is held in the cranking/start position. Some switches don't have power to the Ign until the key is released to run. The drawing is exactly how you connect a Ford Starter relay in a 57 Chevy [and some later years] And it doesn't matter if it has a ballast [not shown in the "Hot" run wire] or an HEI where both wires are spliced together at the HEI coil. Even if a replacement Ignition switch is used [which has 12v Ign while cranking] it will not make any difference. This ^^^ has the option of removing the "I" wire from the starter relay. It started in 1957. 55 and 56 Chevy cars had Ign 1 and Ign 2 on the Ignition switch [one is run and the other is when cranking]
bottom line. i think you want battery voltage to the coil when you’re cranking. then the ballast resistor in the run position.
The smart thing to do would be to purchase a cheap multimeter and find out just what the switch does. put it on the ohms setting, place one lead on to the BAT terminal and turn the switch to find out what's what.
The drawing is correct, it just doesn't mention that the ignition wire from the switch would be ballasted or a resistor wire to drop the running voltage down. The "I" terminal just jumps the coil primary up to full batt voltage when the starter is engaged for hotter ignition when starting
If he's running a big cam and full timing you wouldn't want the coil energised until you get the starter spinning. This works best with the big, factory, hi torque, starters that run faster then the mini starters. These also get the oil pump going sooner..
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