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Old 11-26-2019, 06:16 PM   #9
rotorwrench
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Join Date: Jun 2010
Location: San Antonio, Texas
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Default Re: 12 volt coil with resistor

When the points are closed and the ignition switch is on then the coil is in effect an electromagnet so it does drop some current to maintain the electromagnetic field. This is why some folks end up with a burnt up coil if they forget to turn off the ignition and the points just happen to be closed. The primary will generate a lot of heat and some coils just can't take it.

When Ford changed over to 12-volt in 1956, they added a ballast resister to the system so they could use the same coil but keep the current in check. They did that for a long time. In the modern era, there are a lot better materials for manufacturing ignition coils than there were back when they changed over to 12-volts.

The breaker points can take whatever the system is designed for as long as they have a good condenser to make & break the circuit with. The condenser protects the points and slows the collapse of the magnetic field in the coil core just a bit. This makes for an efficient high tension induction force to the secondary winding and on to the spark plug. Bad condenser equals burnt points and poor or no spark.

Last edited by rotorwrench; 11-26-2019 at 06:23 PM.
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