Thexton THE404 Spark Tester – Compact ignition diagnostic tool, visible arc tester for spark plugs and coil leads

Small enough to fit in a mechanic's pocket or a DIY toolbox, the THE404 offers a straightforward way to confirm whether a spark plug or ignition coil is producing a usable spark without removing spark plugs or risking contact with live high-voltage parts. Designed as an auto accessory, it provides a low-cost, reusable option for troubleshooting misfires, ignition faults, and routine engine checks.

How does the THE404 show whether an ignition system is sparking?

The tester completes a safe, visible path for the ignition current so you can observe spark behavior outside the engine. It is used inline with the spark plug wire or coil lead to reveal the presence and quality of sparks under engine cranking or running conditions.

• Creates a visible arc to indicate ignition firing
• Connects easily to plug wires or coil outputs
• Works during cranking for real-world diagnostics

What are the THE404's physical dimensions and portability?

Thexton designed the THE404 to be compact and easy to store: its package dimensions keep it small enough for tool rolls, glove boxes, or parts trays. Those dimensions also make it simple to maneuver around tight engine bays when checking individual cylinders.

• Package height: 11.988 cm for vertical storage
• Package length: 3.378 cm for narrow fit in tool kits
• Package width: 8.483 cm to take up minimal space

Which vehicles and ignition setups is this tester compatible with?

As a general auto accessory, the THE404 is suitable for most gasoline-powered engines that use conventional spark plug wires or coil-leads. It is intended for basic troubleshooting rather than advanced electronic diagnostics on systems requiring manufacturer-specific adapters or modules.

• Works with conventional spark plug wires and many coil outputs
• Useful across a wide range of cars, motorcycles, and small engines
• Not a substitute for specialized scan tools on modern coil-on-plug systems without adapters

How should I use the tester safely in a garage or roadside setting?

Use the THE404 only with the engine area accessible and the vehicle stable; follow basic safety practices to avoid contact with live electrical parts. Always consult the vehicle manual for specific ignition system cautions and wear protective eyewear when observing sparks.

• Park on level ground and engage parking brake
• Wear insulated gloves and eye protection when needed
• Keep clear of moving parts; observe spark from a safe distance

Who is this for: Thexton THE404 Spark Tester is aimed at automotive DIYers, mobile mechanics, and small repair shops that need a simple, portable way to confirm ignition spark during troubleshooting. It suits users who want a low-cost diagnostic aid for misfires and ignition checks, especially when a quick visual confirmation of spark is preferable to disassembling components or relying solely on error codes.