>A ballast resistor keeps voltage down and makes it easier on coils and
> contact points. If you have a good aftermarket coil and electronic
> "breakerless" ignition then you don't need a ballast resistor. Of
> course, follow the directions of the equipment you use.
> An average car with alternator has about 13.5 volts in the system when
> running. A ballast resistor lowers the voltage through the ignition
> circuit to somewhere around 6-8 volts, which is plenty to run ignition
> systems designed to use a ballast resistor.
NO NO NO. ALL AUTOMOTIVE COILS ON 12-VOLT CARS
REQUIRE A BALLAST.
Some are internally ballasted (3 to 5 ohms across the low-voltage
terminals of the coil) and some are externally ballasted (approx
1.5 ohms across the terminals). In either case, the ACTUAL primary winding
of the coil sees about 9vdc. This is because the laws of physics
mandate that as the primary voltage goes up, the speed at which the
magnetic field can build and collapse goes down. This limits how
high of an rpm the coil can keep up with. It turns out that a 9-volt
primary can keep up with a high-winding 4-cylinder or a good
8-banger, so that is the standard. High-winding V-8 engines tend
to push things a bit, leading to some very creative ignition systems.
Remember the ceramic resistors screwed to the firewall of old Chryslers?
Maybe you ran afoul of the high-resistance "ballast wire" on a Chevy
some time? As pointed out earlier, external ballasts allow you to bypass
them for a hotter spark when cranking. This is less important on smaller
low-compression engines that don't use as much oomph to crank, so it
wasn't much exploited by the Brits, hence our Spridgets came with
internally-ballasted coils which expect to see 12vdc across the coil
terminals (on an externally-ballasted coil you will normally see about
9vdc).
If you are using a Pertronix or Crane, it will expect to see 12vdc where
it connects to the coil, and, since it is using this to power itself, it can
get a bit snotty about it.
It is the condenser that is there to make things easier on the points, NOT
the ballast resistor.
David Lieb
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