Dual Hole Car Plug Tester Detector have two testing holes, you can test two plugs meanwhile and and if you suspect any plug works improperly you could compare and test to make judgment. Usage: Test plug performance and ignition strength Application Range: 12V Gasoline vehicles car plugs Car Plug Test principle: In automobile ignition system, the high-voltage ignition coil generates a high-voltage (10000 volts or more), and the plug diverts it form high-tension ignition coil into the cylinder engine, between the plug electrodes will the mixture. The Detector could tell the good plugs from the bad by the strength of the . Car Plug Tester Using Note: 1. Please Turn Off before you place plug 2. The Plug Tester is a high-voltage detector, so do not touch plug with hand at work to avoid danger. Car Plug Tester User Manual: 1.Place the Plug into tester hole 1 or 2; If you want to compare the new plug and old one, place new plug into hole 1 and the old on into hole 2 2. to supply 3.Turn the key switch 4 clockwise to turn on tester, indicator 3 will light up, tester is now working at 1000rpm/min. 4. Again turn the key switch 4 clockwise,you can adjust the working frequency between 1000rpm to 5000rpm/min. The higher the frequency, the stronger the strength. Main Unit Weight:220G( Not including Adapter) Adapter: Input 100-240V AC / Output 12V 1A DC Colour: black gray Material: plastic Package Contents: 1 * Car Plug Tester 1 * US Plug Adapter 1 * EU Plug Adapter Only the above package content, other products are not included. Note: Light and different displays may the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.