How to Test if the Verna Ignition Coil is Damaged?
2 Answers
Methods to test the Verna ignition coil are as follows: 1. The ignition coil has a primary side with one end connected to the 12v positive terminal, and the other end, known as the cold end, connected to the ignition final stage power amplifier. When starting the engine, the cold end of the primary side should show a voltage jump from 12v to 0v, which can be tested using the voltage range of a pointer multimeter. Observe the needle swing; digital multimeters may show frequent number changes that are harder to observe. The secondary side generates high voltage, and connecting a spark plug should produce a spark. If there is no spark, it indicates the ignition coil is damaged. 2. For ignition coils with built-in ignition drive modules, if the engine control unit sends a normal 0v-5v pulse to the ignition coil control terminal, the ground wire is normal, the power supply is normal, but there is no spark, it means the ignition coil assembly is damaged. 3. Remove and inspect the ignition coil. DC test: primary resistance should be 0.5～1.2Ω, and secondary resistance should be 1kΩ～6KΩ. If the coil contains a high-voltage anti-misfire diode, use the 10k range of a pointer multimeter to check for unidirectional conduction. Note that some ignition coils may show an open circuit in the secondary side but still function normally when installed, as the high voltage can bypass the additional short-circuit gap. 4. Remove and perform a spark test: Use a high-power transistor with the emitter grounded and the base connected to 30-50Ω, intermittently touching the 12v positive terminal. The secondary side should produce a spark. Observe the spark gap distance—higher voltage allows for a larger gap. Also, observe the spark thickness; a thicker spark indicates higher current. Ideally, the spark should be thick, bright white, and produce a crisp, loud sound. Use a diagnostic scanner to read fault codes, which can usually identify which cylinder's ignition coil is faulty.
I've been repairing cars for many years, and testing for a faulty ignition coil is quite simple. You can start with a visual inspection. Check the coil casing for cracks, oil stains, or burn marks—these are common signs of damage. Then, use a multimeter to test the resistance. Set the multimeter to the resistance setting and measure the primary and secondary coil resistances. For a modern Verna, the normal range is between 0.4 and 1.0 ohms. If the reading deviates significantly from this range, the coil is likely faulty. A swap test is also effective: replace the suspected coil with a known good one from another cylinder. If the engine misfire follows the swapped coil, the old one is defective. Don’t forget to inspect the spark plugs and high-tension wires, as they work together—poor contact in any of these can cause ignition failure. If you hear unusual noises or experience weak acceleration while the engine is running, address the issue promptly to avoid increased fuel consumption or damage to the catalytic converter. Finally, I recommend checking during regular maintenance—prevention is the best way to save money.
