I don't think anyone has written a correct reply to this yet. Firstly Lucas
sports coils come in two types each with its own part number - one is for use
with a ballast resistor and one without. From memory one will be a 9V coil
and the other a 12V coil. What happens is that both coils despite having
different input voltage put out the same output voltage - 40,000V or whatever.
However, the 9V coil only sees 9V rather than the 12V the car supplies to it
because the ballast resistor drops the volts by 3 V. But, when the car is
cranked
on the starter motor the ballast resistor is by-passed so that the 9V coils
see the full 12V and produces a much higher voltage than usual. Because the
ballast resistor is only momentarily bypassed no damage is done to the coil and
one the starter is no longer cranking the 9V coil just sees 9V again.
You have to match whatever ignition system you use to your car's coil and if
the coil requires a ballast you have to fit one. On the other hand if you run
a 12V coil with a ballast when you don't need one you are always getting a
weaker spark.
I think this explanation is correct - electrics aren't my strongest thing.
Daniel1312
In a message dated 13/09/06 05:29:30 GMT Daylight Time,
billyzoom@billyzoom.com writes:
>
> All stock 12v systems use a ballast resistor. It can be either inside the
> coil, or outside the coil. If your car has an external resistor, you need a
> coil without internal ballast. If your car doesn't have an external
> resistor, you need a coil with internal ballast. If you have a 6v system,
> you don't need ballast because all stock coils are designed to work with 6
> volts. External ballast systems have a terminal on the ignitions switch to
> bypass the resistor while starting. Internal ballast systems have a thermal
> switch which bypasses the ballast until the coil warms up. There are
> exceptions when using aftermarket systems...for instance, a Pertronix unit
> will not work with an external resistor because the module needs a full 13
> volts to function. The Pertronix coil has to use internal ballast which
> lowers the voltage inside the coil while allowing the module to receive full
> voltage. There are probably other exceptions when using various aftermarket
> ignition systems, but the ballast requirement depends on the coil and not
> the distributor or points.
> BZ
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