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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,274
If you have CDI you should not be getting 12 volts to the coil. You would get pulses of 350 to 450 volts instead, depending on the make of the CDI box.

Now if you have simple points and condensor ignition with no voltage amplifier like a CDI you would have around 10 volts to the coil.
In that ancient type of ignition you should not have 12 volts either because that would burn up the points quickly, so they put in a ballast resistor to drop the 12V down to approximately 10V to keep the points from burning up too fast.

356's and early 912's had simple points and condensor ignition, and I'm not sure if the very first 911's had Capacitive Discharge Ignition or just points and condensor.

The points and condensor ignitons worked by grounding the coil when they close and letting 10-11 volts flow through the coil which created a magnetic field in the primary windings of the coil and when the points opened the magnetic field drops and induces a higher voltage in the secondary windings (which there are much more of) and that higher voltage jumps the plug gap and makes your spark.
The condensor is there to act as a buffer for the points so they last longer.
Old 07-15-2008, 12:03 PM
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