Thexton THE404 Spark Tester — compact inline ignition tester for spark plugs and coils, visible gap, portable 12 cm size

Thexton THE404 Spark Tester is a compact auto accessory that quickly checks ignition spark presence and helps diagnose engine ignition issues.

Thexton's THE404 Spark Tester is a handheld diagnostic aid designed for mechanics, automotive hobbyists, and roadside repairs. Its small form factor and straightforward function let you verify whether a spark plug, coil, or ignition circuit is producing a visible spark without removing components or relying on complex electronic testers. The tool is built for practical, on-the-spot troubleshooting and comes in a compact package sized roughly 12 cm by 3.4 cm by 8.5 cm.

How does the THE404 Spark Tester show whether an ignition circuit is working?

The tester provides a visible spark path so you can determine if voltage is reaching the spark plug or coil. Connect it inline with the spark plug lead and crank the engine; a bright, consistent spark across the tester indicates ignition activity. It’s a simple optical confirmation rather than a digital measurement.

• Visible gap that lights when voltage is present
• Inline connection for plug leads or coil towers
• Quick confirmation without disassembly
• Safe for spot checks if used as directed

What connectors and sizes does the THE404 fit?

Thexton designed this accessory to be broadly compatible with common automotive ignition components. It fits most standard spark plug leads and coil boots used on gasoline engines. For specialty or high-performance ignition systems, verify physical fit before use.

• Works with typical spark plug boots and ignition leads
• Compact body to access tight engine bays
• Suitable for many passenger cars and light trucks
• Check compatibility for unconventional ignition systems

How do I use the tester safely to avoid damage or injury?

Always follow basic ignition safety: engine off while making connections, insulated grips, and keeping flammable materials away. Only crank the engine briefly while holding the tester in position and using protective gloves or insulated tools if needed. Avoid prolonged exposure to sparks and keep hands and conductive tools clear of the gap.

• Make connections with the engine off, then crank briefly to test
• Use insulated gloves and keep clear of moving engine parts
• Do not hold the tester against metal surfaces during testing
• Store in a dry place to preserve insulation and visibility window

What size is the THE404 and how portable is it for fieldwork?

Thexton THE404 packs into a small footprint that’s easy to carry in a tool roll or glovebox. Its package dimensions are approximately 11.988 cm in height, 3.378 cm in length, and 8.483 cm in width, making it one of the more compact spark-check tools suitable for roadside diagnostics.

• Package height around 12 cm for easy storage
• Low-profile length and width for tight compartments
• Lightweight and simple to slip into a toolbox or bag
• Ideal as a quick-check tool in mobile toolkits

Who is this for: Thexton THE404 is aimed at DIY mechanics, professional technicians needing a quick verification tool, and drivers who want a compact item for emergency troubleshooting. If you perform routine ignition checks, repair older vehicles, or need a fast way to confirm spark without complex meters, this tester is a practical addition to your kit. It is not a precision voltmeter or timing instrument; rather, it’s a straightforward visual tool for confirming whether an ignition circuit is producing a spark.