Accessory guideIgnition Coil Tester

This guide gives you a complete, practical method for using an ignition coil tester to diagnose coil faults quickly on the vehicle, covering the tool's purpose, the main types available, safe connection, step-by-step testing, and how to interpret the readings you obtain. It is written for working mechanics and experienced DIYers who already understand basic ignition theory and want a repeatable, evidence-based approach rather than guesswork. You will learn to distinguish a failed coil from a spark plug, wiring, or control module problem using resistance, current ramps, and spark quality checks, with worked examples and real diagnostic jobs. After finishing, you will be able to set up the tester safely, run tests on several coil designs, read the results with confidence, and know when a fault exceeds the scope of on-vehicle testing.