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Discussion Starter #1
can someone tell me what voltage reading I shoud get at the coil and the starter solenoid ignition terminal? 1963 galaxie 289 Thanks
 

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Hey Tom - The voltage at the coil (+) terminal and solenoid "I" terminal will always be the same, as they are directly connected after the fat pink resistor wire. Test terminology is:

  • KOEO (Key On Engine Off)
  • KOES (Key On Engine Starting)
  • KOER (Key On Engine Running)
When testing the following results are typical:

  • KOEO: voltage = battery voltage (coil wire disconnected)
  • KOES: voltage = battery voltage (coil wire connected or disconnected)
  • KOER: voltage = 6 to 9 volts (coil wire connected)
Is that what you're looking for?

David
 

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Discussion Starter #3
Thank you for your reply. KOEO at "I" was 7.2 volts, but voltage at coil was only 5.8. Maybe time for new wiring. The resistor was put in to intentionally drop primary voltage to the coil? I'll check when able with engine running. Thanks Tom G
 

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Thank you for your reply. KOEO at "I" was 7.2 volts, but voltage at coil was only 5.8. Maybe time for new wiring. The resistor was put in to intentionally drop primary voltage to the coil? I'll check when able with engine running. Thanks Tom G
Tom, I have a wiring diagram of the basic circuit I'll post when I get to the other computer, but the "I" terminal and coil are on a Y-wire, joined at the firewall. The "I" wire is usually BROWN and the coil wire usually RED/GRN. Between the firewall and the key switch is the PINK resistor wire. The purpose of the PINK wire is to reduce current through the coil, and in doing so, also reduces the voltage when under load. If the circuit is not under load, the wire should show full battery voltage.

So, KOEO would have full battery voltage through the firewall to both terminals. As there is no load, you see full voltage. However, if you have points or certain 'dumb' points-replacement electronic ignitions, and the points or circuit happen to be closed (charging the coil), you will see lower voltage than the battery. My bad - I should have listed the "what if". Test again after disconnecting the coil (+) wire to verify full battery voltage at the disconnected end of the coil wire.

When the car is cranking in KOES, the starter relay (solenoid) closes contacts and sends full battery power out the "I" terminal to the coil for better spark during starting. This bypasses the PINK resistor wire during cranking only. Again, you should see battery voltage, though the entire system will be lower voltage due to the starter load.

Once running, and the start relay disengages, coil power is through the PINK wire only. The effect is to lower the available power to the coil, giving a running voltage of 6 to 9 volts. Why? Because we really would like full battery voltage to the coil at all times, but if the car stalls or the key left KOEO for any reason and the points are closed, the coil will cook at full battery power. So, the PINK wire is used to ensure it doesn't fry. That is the sole purpose of the resistor wire and the need for the "I" terminal.

You can see how a change to a 'smart' electronic ignition module could simplify the wiring, while improving spark during KOER, and still protect the coil when KOEO.

David
 

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Discussion Starter #5
Thanks David I had a wiring diagram once but can't locate it. I'm letting all of this sink in. i'm more mechanical than electrical type person. I'll do some more voltage checks tonite after work. The whole wiring is 1963 original and may not be in the best of shape anyway. Things work, but all this came up after deciding to install a Pertronics Ignitor I points replacement module, and wanted to make sure it had enough voltage not to drop out. Nevertheless, this is all very interesting and hopefully informative to other Ford people who want to really understand the original technology and engineering.
 

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Here's that diagram I drew. Hopefully the description will mesh with it to make the full picture for you.

David

Typical Ford stock points wiring. "Dumb" electronic conversions (PerTronix 1, DuraSpark II, etc.) will use the same setup. "Smart" ignitions (PerTronix II and III, DuraSpark I, and most others with dwell control) can delete the resistor and solenoid wires:

 

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Discussion Starter #7
David, the wiring diagram was helpful. Thanks. Everything is working ok. I'm replacing my old carb with a new one with electric choke. A friend here in Texas told me that when he did the same, he added a relay underhood with two accesory outputs ( full 12 volts ) to the coil and the choke. Sounds pretty slick, but I don't have the details yet. Have you done the same or have experience with this. It also seems to me that replacing the pink resistance wire with regular wire would then let me have 12 volts to coil and also use the "I" lead at starter solenoid to power the electric choke. Maybe I should just run a separate switched wire to the choke, and quite worrying about potential low coil voltage that could cause the Pertronix Ignitor to drop out. Anyway this is all very interesting from an educational standpoint, if for no other reason. Thanks for your help
Tom G
 

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If you have a PERTRONIX (preferably PERTRONIX II), I think you will find the module wants full BAT VOLT. It will run on the resistor wire but not as well. To use a coil with full BAT VOLT, it has to be marked NOT FOR USE WITH EXTERNAL RESISTOR. This precludes the OEM coil. You need a coil with an INTERNAL RESISTOR (PERTRONIX offers one) or wire the OEM coil through the resistor wire.

The best way to supply BAT VOLT is with an external fused relay. Power the FULL ELECTRIC CHOKE from another relay. This way if you ever want to return to OEM, the resistor wire will still be in the harness and the harness will not be tampered with.

Simply put, the "I" circuit provides full BAT VOLT to the IGN for quick start and once the key is released to RUN, the current will be supplied through the resistor wire (in this case) and as the resistor wire heats, it creates resistance.
 
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