asdfg@ihnss.UUCP (06/03/83)
The ballast resistor, whether a separate resistor
mounted on the firewall as in Chrysler products,
or resistance wire as used in older General Motors
products, is used to limit the maximum current
through the ignition coil during normal engine
operation.
During engine starting, the starting motor draws a
large amount of current, and the voltage available
for the ignition coil is less than the voltage
during normal running. Since more current
translates to a higher spark voltage, this is
exactly what we need during starting, especially
cold weather starting. Once the engine is running,
the spark voltage does not need to be as high, so
resistance is added to the primary circuit.
When the ballast resistor fails, the engine can be
started, but as soon as you let go of the key, the
engine will die. The resistor can be bypassed in
an emergency to get the engine running, but the
increased current through the points can cause
early point failure. The coil would also run
hotter than normal, and this emergency procedure
should not be used for a long period of time.
Roger Johns