1. There are two test holes, which can test two spark plugs at the same time. If you suspect that any spark plug is not working properly, you can compare the tests to make an accurate judgment.
2. Adjustable Dual Hole Automotive Spark Plug Tester Detector Spark Plug Analyzer Diagnostic Tool
3. Purpose: Test spark plug performance and ignition strength
4. Scope of application: spark plugs for 12V gasoline vehicles
5. Operating temperature: -10 to 40 degrees Celsius
6. Dimensions: 145x85x113mm

Auto spark plug tester user manual:
1. Put the spark plug into test hole 1 or 2; if you want to compare the new spark plug with the old spark plug, put the new spark plug in hole 1 and the old spark plug in hole 2
2. Close the protective cover and plug the adapter into the side receptacle to connect the tester to a power source.
3. Turn the key switch clockwise to turn on the tester, the indicator light will turn green
4. Continue to turn the switch clockwise to adjust the operating frequency between 1000rpm and 6000rpm/min. The higher the frequency setting, the stronger the spark.