Review on Tool Aid 23970: In-Line Spark Checker 🔌 Kit for Recessed Plug - Efficient Troubleshooting Tool by Luke Cotton

Perfect match for my Mercedes. I had a bad coil that was misfiring according to my diagnostic app called HobDrive. Not knowing how to determine which of the 3 coils was correct, I figured this tool would help me figure it out. When I received it I noticed that it is such a simple but well thought out tool. One thing I found a bit odd was that they shipped it in a box and just put a shipping label on it. At least everything was still there when I got it, so everything is fine. When using this I only used the coil tester and coil tester extension cable as my car has recessed spark plugs. I connected it to each spark plug and started the engine every time. I found that the light was bright on 4 and dim on 2 connected to the same coil! I replaced the coil and the new coil lit the bulb brightly as did the other coils. Then my app showed no dropouts and now the car is running smoothly again. I'm not sure if this tool will tell you if the spark plugs themselves are bad. I'm assuming the light only flashes when the spark plug is good, so I didn't bother with that. I might buy a plug tester someday, if not soon. This saved me an expensive fee having to take it to a mechanic for diagnosis.