This fully potted, weatherproof module can be wired into the power supply of a coil per cylinder ignition system, where it senses current and creates a conventional 12V square wave signal output which can be utilized by AutoMeter tachometers and many aftermarket RPM activated devices. Ideal for vehicles with late model engine swaps and applications where conventional tachometer signals are not available. Tachometer Adapter Distributorless Ignitions Each. Auto Meter 2189 LS Engine Plug & Play Wire Harness For #9117 Tach Adapter NEW.