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Several questions and comments on resistors has
piqued my "response syndrome". I've got to answer! I'm
COMPELLED!. It's not really my fault, I'm just a former schoolteacher
who's not asked about these old things anymore.
The Ignition Resistor is called a "Ballast
Resistor" simply because it's encased in porcelain so it will not burn up when
it gets hot. The reason it's designed that way is so that it can get VERY
hot, and, as many of you know, when heat in a conductor goes up, the resistance
increases, and current flow goes down, and voltage is used up. In the
point style ignition system this means that less current is sent across the
points, so that the condensor can more easily controll the sparking at the
points. When the engine is running slowly, the time that the points are
closed is greater, and the points would heat up too much, and burn out
quicker. But when the engine is running faster, the time of current flow
through the points is shortened, and therefore the ballst resistor can cool down
a little, allowing more curent flow through the points, and maintaining a good
magnetic field in the primary coil.
There are other resistors in the Generator
Regulator, though. The Field strength of the generator magnetic field is
controlled by passing the field current throught magnetic switches in the
regulator (those two little clicker switches inside*). By sending the field
current through these resistors some of the time, the field current can be
controlled to maintain maximum allowed voltage and amperage output from the
generator.
*Actually there are three little magnetic switches
inside the regulator. They are the Voltage sensitive regulator, the
Current sensitive regulator, and the Cut-Out switch, which is designed to
disconnect the generator from the battery when the car is not running, so the
battery will not drain through the generator..
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