frankieflathead Posted May 10, 2013 Report Posted May 10, 2013 (edited) Been thinking about the spare parts I want to have with me now that the car show season is officially upon us up here. Aside from tune up parts, I thought it might be smart to carry a spare coil, but for the life of me I can't remember if I need a resistor or non resistor coil in my D24. Can't make out the markings on the one in the car and it's running fine right now. Local parts store has one with an internal resistor for $20 and that seems like a great price. I'm currently running Champion J11C non resistor plugs in the car and it may very well have old style copper core wires on it. Checked the tech section here and found nothing on the subject, and my factory shop manual reprint just says use OEM. HA! Do I need to run a non resistor type coil, too? Edited May 10, 2013 by frankieflathead Quote
TodFitch Posted May 10, 2013 Report Posted May 10, 2013 It is my understanding that you only need a coil with internal resistor if you are running a 12v system with out an external ballast resistor. Quote
frankieflathead Posted May 10, 2013 Author Report Posted May 10, 2013 It is my understanding that you only need a coil with internal resistor if you are running a 12v system with out an external ballast resistor. Thanx Tod, but since this is a 6 volt coil with an internal resistor is there any reason why I can't use it with my stock 6 volt ignition system? Will it provide sufficient power or harm my stock points and/or condenser it any way? Quote
DCurrent Posted May 11, 2013 Report Posted May 11, 2013 A six volt coil will work fine. How do you know it has a internal resistor in it? If I understand the job of a coil correctly a six volt coil doesn't have a resistor in it because it only puts out 6 volts which is the correct voltage to go to the points. a 12v coil needs a resistor or a special wire to limit the output to 6v or the points will fry. That's in layman's terms anyway. I'm sure someone else may have a more electrical background and can explain the specifics. Darren Quote
_shel_ny Posted May 11, 2013 Report Posted May 11, 2013 If you want a spare make it easy on yourself. NAPA MPE IC7SB 6 volt coil Shows $16.49 at my local NAPA Quote
Plymouthy Adams Posted May 11, 2013 Report Posted May 11, 2013 12 volts will overheat the coil due to the very current that will be felt on the coil as it's internal resistance is set (wound) for 6 volt operation, double the voltage and basically double the current and overheat the coil..additional heat draws geater current and next thing you know you in thermal runaway....thus the idea of the dropping resisitor to continue using an industry standard with the newer voltage requirement. The points are just the means of grounding the coil primary circuit..and their closed duration (dwell is the time of the points are closed). The position of the distributor times this electrical function to the fixed mechanical workings. Longer the dwell the greater the saturation and hotter the spark to the extent of applied voltage. Of course points can see speedy erosion of the contact surface due to higher voltage and if ignition is left on and the points are closed and engine is not running..When the points open it is the collapse of the primary winding that causes the spark from the coil's secondary windings..that is sent to the input of the distributor cap and of course depending on what cylinder is set to fire what tower the rotor places the spark out to that plug. The points are protected also by the condenser that provides an alternative path to ground for the voltage when the points start to open and prevents a spark gap that would burn the points..this also serves for radio interference during the opening and closing of the points... so you have one of there choice for these older coils....6 volt (no resistor needed) which is but the 12 volt with external resistor or the 12 volt internal resistor....the external resistor can be a resistance wire in the harness or a resistor itself. Quote
frankieflathead Posted May 11, 2013 Author Report Posted May 11, 2013 A six volt coil will work fine. How do you know it has a internal resistor in it? If I understand the job of a coil correctly a six volt coil doesn't have a resistor in it because it only puts out 6 volts which is the correct voltage to go to the points. a 12v coil needs a resistor or a special wire to limit the output to 6v or the points will fry. That's in layman's terms anyway. I'm sure someone else may have a more electrical background and can explain the specifics. Darren Thanx, Darren. I know it has an internal resistor because it says so right on the coil. Quote
frankieflathead Posted May 11, 2013 Author Report Posted May 11, 2013 12 volts will overheat the coil due to the very current that will be felt on the coil as it's internal resistance is set (wound) for 6 volt operation, double the voltage and basically double the current and overheat the coil..additional heat draws geater current and next thing you know you in thermal runaway....thus the idea of the dropping resisitor to continue using an industry standard with the newer voltage requirement. The points are just the means of grounding the coil primary circuit..and their closed duration (dwell is the time of the points are closed). The position of the distributor times this electrical function to the fixed mechanical workings. Longer the dwell the greater the saturation and hotter the spark to the extent of applied voltage. Of course points can see speedy erosion of the contact surface due to higher voltage and if ignition is left on and the points are closed and engine is not running..When the points open it is the collapse of the primary winding that causes the spark from the coil's secondary windings..that is sent to the input of the distributor cap and of course depending on what cylinder is set to fire what tower the rotor places the spark out to that plug. The points are protected also by the condenser that provides an alternative path to ground for the voltage when the points start to open and prevents a spark gap that would burn the points..this also serves for radio interference during the opening and closing of the points... so you have one of there choice for these older coils....6 volt (no resistor needed) which is but the 12 volt with external resistor or the 12 volt internal resistor....the external resistor can be a resistance wire in the harness or a resistor itself. Thanx, Tim. I'm looking at a six volt coil that's marked "internal resistor". Quote
frankieflathead Posted May 11, 2013 Author Report Posted May 11, 2013 If you want a spare make it easy on yourself. NAPA MPE IC7SB 6 volt coil Shows $16.49 at my local NAPA Eezy, peezy. And cheap, too. Nothing like a part number to simplify things. I'm assuming that you have real world experience using these. Thanx, Shel. Quote
Don Coatney Posted May 11, 2013 Report Posted May 11, 2013 Frankieflathead; You have a 6 volt system. You need a 6 volt coil without an internal or external resistor. End of story. Quote
Solution frankieflathead Posted May 11, 2013 Author Solution Report Posted May 11, 2013 Frankieflathead; You have a 6 volt system. You need a 6 volt coil without an internal or external resistor. End of story. That's what I thought, Don, but I wasn't 100% sure. Like you say, that's one marble that had partially fallen out of my bag. Thanx, 1 Quote
_shel_ny Posted May 11, 2013 Report Posted May 11, 2013 Eezy, peezy. And cheap, too. Nothing like a part number to simplify things. I'm assuming that you have real world experience using these. Thanx, Shel. Have not had occasion to purchase the NAPA one as I have a NORS coil on the shelf in the garage. You would have to look at the package to be sure it suits your needs Quote
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