Can a Bosch ignition coil change its primary resistance?

Now that I've got my timing correct, I'm investigating issue #2.

In the final 1000 miles of my 7000 mile trip, the engine became harder to start each morning.

The issue seemed to be the ballast resistor (1.8 ohm Bosch). Remove the resistor from the ignition circuit, and engine starts and runs perfectly.

But today I decided to check the ignition coil. Bosch "red" coil; spec is 1.8 ohm primary, 12K ohm secondary.

My coil's primary measures 2.5 ohms. How'd that happen?

I wonder if this increased coil resistance, added to the ballast's resistance, causes voltage to drop below "sparking" level for the cylinders.

Battery voltage: 13.5v.
Voltage to coil without resistor: 13.5v.
Voltage to coil *with* resistor: 5.1v.

Note: for the entire 7000 mile trip I had the wires ignition and distributor wires attached backwards on the coil.

Thanks.
Tom
1960 190b

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