How do you test 9n ford coil?

To test a 9N Ford coil, first ensure the ignition switch is off and disconnect the coil from the ignition circuit. Then, use a multimeter to measure the primary resistance by checking across the two terminals; a typical reading should be between 1.5 to 3.0 ohms. Next, perform a secondary resistance test by measuring across the high-tension output terminal and the ground; this should usually be around 7,000 to 10,000 ohms. If the readings are outside these ranges or if there are signs of physical damage, the coil may need to be replaced.