Most 12V car coils [on distributor ignition systems] are designed to run with a 'ballast resistor' in the +ve supply.
So in normal running the coil sees ~8V. However, when the starter is engaged, the resistor is bypassed to make up for the voltage drop due to the starter draw.
Cheers,
Gadge
"ODK Mods can explain it to you, but they can't understand it for you..."
"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."
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