Using the guidance offered, for which thanks, I’ve come to the conclusion that I don’t have a ballast resistor. Wires from the coil connect to the distributor or straight into the wiring loom which disappears (or appears, depending on which way you are tracing it) into the bulkhead by the fuse box.
Not sure what this means for the spec for the coil, if I’m to replace that, but if I can get it off I might be able to find some identifying codes on it.
Mark
Ballast coil is usually rated at 9 volts whereas non-ballast is 12 volts. Often, there is a label saying “use with ballast”. If no identifying marks, there are two alternatives. Have a multimeter ready, set on DC voltage range, and switch on ignition, but do not start engine. Measure voltage between + terminal (or “sw” terminal, if so marked) on coil to earth. If it’s a ballast type it should read about 9 volts; if not then 12 volts or so. Alternatively, disconnect small wires from coil and measure its resistance across the two small terminals. A 12 volt coil will be about 3 ohms whereas a ballast one will be about 1.5 ohms. (Approx figures, as the test leads themselves will present some resistance depending on length and diameter.)
