Now you can easily determine if the gauges in your car are working properly. The TL-GT001 Gauge Tester lets you verify the high, medium, and low reading for your gauges and also displays that the Instrument Voltage Regulator is working. Will work on any Ford, Lincoln, or Mercury with a 73-10 Ohm range from 1955 to 1986. Perfect for any toolbox!Testing As Easy As 1-2-3 Simply hook the red lead up to the sender wire, and the black lead up to the ground, turn the key to the ACC or RUN/ON position and you’re ready to begin testing. If the gauge works -- you have a faulty sender. If the gauge doesn’t work -- you have a problem with your sender and/or wiring. Power Test Power light will flash when powered on if a mechanical voltage regulator controls your gauge cluster. If a solid state regulator has been installed as a replacement, the power light will illuminate without flashing.