I've searched thru dozens of old posts and it's just making me dizzy, so I'll ask. With an all 6 volt system, do you need to have resistance to the coil? I've seen that resistance can be built into the coil, built into a wire, or from a ballast resister. Specifiallcy for me, I have a 48 GMC truck, original 6v positive ground system, it has a 6 volt battery, 6 volt coil, original distributor. It doesn't look like the wire to the coil has resistance, there is no ballast resistor, I need to replace the coil, do I have to get a coil with resistance built in or use a ballast or just get a basic replacement 6v coil with no resistance?
found this.. quite neat actually http://chevy.oldcarmanualproject.com/electrical/wiring/index.htm no ballast so its either internally ballaced or not ballasted, i think its non ballast. squirrel would be the one to answer that question...
No most coils are designed to work at about 6 volts input. 12V cars use resisted inputs or internally resisted coils (usually clearly labled as such) to keep the coil from over heating. Some starter solenoids, like ford 12v have an unresisted terminal that feeds the coil 12 v while the starter is spinning. theory is to give a hotter spark while starting the engine. Then when the key is released, the circuit goes through the balast resistor or the resistor wire. So a 6v car will run on just about any coil you mount that is not lables as internally resisted. The resistor in the 12v system usually operate the coil at 7 or 8 volts. The important thing is to ***ure the coil is wired properly for the grounding system of the vehicle. Most 6V were positive ground. so from ign the wire should go to the egative coil terminal and the positive terminal to the points, where the circuit gets grouded to positive when the points open. Opposite for negative grounded circuits. As a point of reference in regard to resistance, it is the most usualy reason why 6 V systems do not operate as designed. Any resistance in a circuit kills the electrical flow (amps) which 6 V system depend upon for proper operation. The most usualy place is a corupted ground after the load or loose or corupted connections in front of the load. The other most usual suspect is that the #1 gauge or thicker main battery cables have been replaced with the wimpy stuff 12V likes , and the ground strap from the body to the frame or engine is missing. One reasons that manufacturers switched to 12V is that they could half the gauges of wires used in the vehicles circuits. Saving weight but more important saving money.
Off hand I can't think of a 6 volt ignition that has a resistor. That seemed to come in with the 12 volt systems, they had a resistance wire in the harness or a ceramic body resistor on the coil circuit.
It's all about the coil, not about the car. Some 6V coils need resistors and some don't. Some 12 V coils need resistors, some don't.
The reason for the ballast resistor is the voltage drop at cranking. A coil could be wound to operate on any voltage without a ballast. Ballasted systems generally have a byp*** circuit to feed the coil full voltage when the engine is cranking, to provide a hotter spark. On some cars, there are actually two ignition circuits, and when the ballast resistor fails it will fire cranking then die as soon as you release the key. B.
I think you will find ballast resistors in all Ford ignitions through 1948, maybe through 1955.......the end of their 6 volt systems
I have a couple old Mallory 6V coils with built in .7Ω resistors. I think it depends on the design of the coil and the resistance of the primary windings regardless of voltage. I have an old tune up manual from the '40's, and it says a quick test is to connect a voltmeter from the distributor terminal on the coil to a ground. With the engine idling at 500 RPM and the correct dwell, you should see about 3 volts in a 6V system. This is very imprecise, but they were interested in point life. Lower voltage you needed some more resistance, or the primary windings were shorted or grounded. Hope this helps.
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