Review on ENA Universal In-Line Spark Plug Engine Tester for Automotive, Car, 🔌 Lawn Mower, Truck, Chainsaw, Motorcycle - Compatible with 6-12 Volt Fool-Proof Operation by Jeffrey Mosqueda

Does not get a zero because it fires the connected spark plug. I don't know anyone who would work in complete darkness without a breakdown. Fixed lawn mower outside in daylight. Even in the shadows, no light is visible. In addition, ***DANGER*** When the shoe is plugged into an AC outlet, it will have approximately 1.5 inches of bare metal. For those not into bare metal, this is synonymous with high voltage.