The Ford Barn

cycleguy79 · 10-20-2016, 02:44 PM

I have a 52 customline with a 12 volt conversion. Last night the ignition coil literally blew the top off and oil went everywhere. My first question is why? It was a 6V so I switched it now to a 12 Volt. When I go to put the new coil in the damn car wont start now. I have spark at the points, but not at the plug wire going to the distributor. Its a 3 wire system - 1 wire come from the drivers side firewall, 1 wire from what look like a resistor and another wire coming from the bottom of the distributor. Where do these wires go on the coil?

flatheadmurre · 10-20-2016, 03:19 PM

If you put in a 12v coil for use without a resistor and you have the old resistor still there it won´t work very well...that was my first thought.
Take the resistor out or make sure it´s the correct one for the coil you put in.
The wire coming from resistor is the feed and should go to + on coil(assuming you have neg ground)
The wire from distributor should go to - on coil.
The wire from firewall....could it be for a tachometer ??

Ross F-1 · 10-20-2016, 05:24 PM

Was your solenoid changed out to a more modern 12v type with two big terminals and two small ones? If so, those have a small "I" terminal that feeds the coil straight 12v during cranking, bypassing the ballast resistor.

rotorwrench · 10-20-2016, 05:35 PM

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The coils are more concerned with the amperage they draw than what the system voltage is. The coils for the early 12-volt systems used a ballast resistor to keep the heat out of the coil and stabilize the current flow to the primary coil winding. More modern coils use different materials for dielectric inside the coil and can take a lot more heat than the ones back in the day but they tend to have a higher primary coil resistance than the old ones do. That's why they don't need an external ballast resistor. You just need to know what you have. Most coils have notes printed on the outside of the can that let you know whether it requires an external resistor or not.

Most 12-volt systems have negative ground or earth connections. The old coils were connected backwards (with positive ground) compared to the way a modern negative ground system is connected. Later 12-volt systems all used the + terminal for power in from the ignition switch and - terminal for a connection to the distributor breaker points.

You may need a test light or better yet, a volt meter to tell what you have coming from the ignition switch.

10-20-2016, 02:44 PM	#1
cycleguy79 Junior Member Join Date: Oct 2016 Posts: 1	215 6 Cylinder Ignition Coil Wiring I have a 52 customline with a 12 volt conversion. Last night the ignition coil literally blew the top off and oil went everywhere. My first question is why? It was a 6V so I switched it now to a 12 Volt. When I go to put the new coil in the damn car wont start now. I have spark at the points, but not at the plug wire going to the distributor. Its a 3 wire system - 1 wire come from the drivers side firewall, 1 wire from what look like a resistor and another wire coming from the bottom of the distributor. Where do these wires go on the coil?

10-20-2016, 03:19 PM	#2
flatheadmurre Senior Member Join Date: Apr 2015 Location: Sweden Posts: 3,045	Re: 215 6 Cylinder Ignition Coil Wiring If you put in a 12v coil for use without a resistor and you have the old resistor still there it won´t work very well...that was my first thought. Take the resistor out or make sure it´s the correct one for the coil you put in. The wire coming from resistor is the feed and should go to + on coil(assuming you have neg ground) The wire from distributor should go to - on coil. The wire from firewall....could it be for a tachometer ??

10-20-2016, 05:24 PM	#3
Ross F-1 Senior Member Join Date: Nov 2010 Location: NM Posts: 2,438	Re: 215 6 Cylinder Ignition Coil Wiring Was your solenoid changed out to a more modern 12v type with two big terminals and two small ones? If so, those have a small "I" terminal that feeds the coil straight 12v during cranking, bypassing the ballast resistor. __________________ '52 F-1, EAB flathead

10-20-2016, 05:35 PM	#4
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,432	Re: 215 6 Cylinder Ignition Coil Wiring Sponsored Links (Register now to hide all advertisements) The coils are more concerned with the amperage they draw than what the system voltage is. The coils for the early 12-volt systems used a ballast resistor to keep the heat out of the coil and stabilize the current flow to the primary coil winding. More modern coils use different materials for dielectric inside the coil and can take a lot more heat than the ones back in the day but they tend to have a higher primary coil resistance than the old ones do. That's why they don't need an external ballast resistor. You just need to know what you have. Most coils have notes printed on the outside of the can that let you know whether it requires an external resistor or not. Most 12-volt systems have negative ground or earth connections. The old coils were connected backwards (with positive ground) compared to the way a modern negative ground system is connected. Later 12-volt systems all used the + terminal for power in from the ignition switch and - terminal for a connection to the distributor breaker points. You may need a test light or better yet, a volt meter to tell what you have coming from the ignition switch.