The double hole car spark plug detector has two test holes, you can test two spark plugs at the same time, if you think one spark plug is not working properly, you can compare and test to make a correct judgment. Used to test spark plug performance and ignition strength, suitable for spark plugs on 12V gasoline vehicles.&lt; /p&gt; Adjustable Dual Hole Car Spark Plug Tester Glow Plug Analyzer Diagnostic Tool Advantages of Dual Hole Car Spark Plug Detector for Automotive Spark Plug Tester:< br/> The double hole car spark plug tester has two test holes, you can test two spark plugs at the same time, if you think one spark plug is not working properly, you can compare and test to make a correct judgment. Purpose: to test the performance and ignition power of the spark plug Area of use: spark plug for 12 V gasoline vehicles. The principle of testing spark plugs in cars: In a car's ignition system, a high voltage coil generates a high voltage (over 10,000 volts), which is converted into high voltage electricity through the spark plug. The high voltage ignition coil enters the engine cylinder, sparks are generated between the spark plug electrodes and the mixture is ignited. The detector can tell The quality of a spark plug depends on the strength of the spark. Precautions for using the car spark plug tester: < br/> 1. Turn off the power before turning on the spark plug 2. The spark plug tester is a high voltage detector. Do not touch the spark plug with your hands during work to avoid danger. Car Spark Plug Tester User Manual: 1. Place the spark plug into test hole 1 or 2; If you want to compare the new spark plug and the old spark plug, insert the new spark plug into hole 1 and the old spark plug into hole 2. 2. Connect power 3. Turn the key switch 4 clockwise to turn on the tester, the indicator light 3 lights up and the tester runs at 1000 rpm. 4. Turn the key switch 4 clockwise again to adjust the working frequency between 1000 rpm and 5000 rpm. The higher the frequency, the stronger the spark intensity. Product parameters of the spark plug tester for gasoline vehicles: L size 'host: 145*85 *60mm Host weight: 220 G (excluding power ) Power : 100-240 V AC input / 12 V 1 A DC output. Set Spark plug tester for 12V petrol vehicles includes: Spark plug tester 1 Piece 1 power