The coil doesn't determine weather you need a resistor, the dist. does. On my MSD electronic plug and play dist. it says you do not need one, but I called the tech hotline anyway and they confirmed it. Just give them the model # of your dist. and they'll tell you. That's right from MSD. I've been running mine for a couple of months now and no trouble.
Usually the ballast resistor was put in place to make the points last longer in a points distributor... the lower voltage would extend the life of the points....GM used actual resistors, many Fords use a special "resistor wire"..... Most, if not all, electronic distributors you can eliminate the resistor and supply a full 12 volts to the distributor. Tom
The ballast resistor is there to make the coil perform correctly at start up. Your coil is usually about a 9 volt unit, and when the motor is running it has its power supply routed through the ballast resistor. When you are cranking the starter motor the system voltage is sapped down to about 9 volts due to the load, so the ballast resistor is switched out of the circuit and you get full system voltage to the coil: about 9 volts. Perfect, you get a nice fat spark. Thus the coil is running at 100% efficiency for starting. Once the motor is running the ballast resistor switches back into the coils power supply and away you go, coil running on normal 9 volts again. The switch for this is usually/often part of the starter motor.
not true - the combination of the Coil and the Distributor determine whether or not you should use a ballast resistor - Coils generally come in resistance factors of anywhere from close 0Ω to 3 Ω plus. And it is the combination that makes it all work, or not.
Well, with an Accel coil and what seems to be an electronic MSD dizzy, she will not idle with the ballast resistor wired in. I've been driving it around for a while and it seems fine. It came to me barely running. It had a very small MSD coil which I believe to be for drag racing only (doesn't have ample cooling abilities for constant driving)
OK, this thing's pissing me off. I took off the drag coil and put the Accel on. Runs fine, but won't idle w/ballast res. So I remove it. Runs fine. I drive it around for a 1/2 hour, no probs. Customer picks it up and he can't get 1/2 mile without it dying @ idle (runs OK otherwise). I change the coil and it idles fine, but I put the Accel back on within 10 seconds and it idles too. Can either coil be stressing something in the MSD distributor?
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