Electrical help


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By Kahuna - 15 Years Ago
I'm converting my car to 12 volts. I have a 12 volt solenoid but am unclear on how to hook it up? I know the large terminal are for the battery and starter, but then there are two smaller posts on it. I'd like to know what goes where on those?

Thanks for any assistance

Jim

By 55Birdman - 15 Years Ago
Coil and ignition switch I believe.
By Speedbump - 15 Years Ago
If you look carefully at the two small terminals, most will have an "S" and an "I" cast in the plastic by the respective terminal.  The S terminal gets a wire from the start terminal of your ignition switch as it activates the relay when the ignition is turned to start.(spring loaded)  The I terminal is a power out of full battery voltage that can go to the ignition coil positive terminal.  It's function is to provide full voltage to the coil/breaker points during the cranking process for a hotter spark.  Once started, the coil/breaker points only want about 9V from the ignition switch going through an ignition resistor.  If you convert to most electronic ignition conversions, you can leave that terminal unconnected.
By Kahuna - 15 Years Ago
Thanks so much, guys. That's exactly what I needed to know. I really appreciate it

Regards

Jim

By GREENBIRD56 - 15 Years Ago
This diagram shows the way the 12v systems came from Ford.

The "Hot in Start" wire is going to the "S" terminal - and it is typically coming to the solenoid from a "Neutral Start" switch. The "Jumper" from the second terminal provides direct battery voltage to the coil (around the ballast resistor) to keep the coil voltage up as high as possible when the voltage "sags" under the starter load.

The voltage in the "Ignition ON" wire is often reduced below battery voltage due to all of the connections and small size wire it goes through getting out to the ballast resistor - so there can be some advantage to having the jumper even when the ballast resistor has been omitted.

By Kahuna - 15 Years Ago
Thanks very much Steve. I think I can now make it work

Regards

Jim

By rick55 - 15 Years Ago
Everything everyone has said previously is correct.

If you are converting to 12 Volts you will not have a ballast resistor already in the ignition circuit, so if the coil or ignition system you are using calls for one you will need to connect one as per the diagram.

ACCEL systems require the ballast resistor, most Pertronix don't. Be sure to check the product information before you hook it up.

If you are hooking it up with points it is probably better to run the coil which needs a ballast resistor and the wire from the solenoid as it will start easier as the solenoid bypasses the resistor when starting.

Regards

Rick