Calterm Tru-Spark Ignition Firing LED Indicator Tester — Green/Red, Adjustable Sensitivity, Non-Contact

The Calterm 66331 Tru-Spark is a non-intrusive ignition firing indicator that shows secondary voltage pulses with a green power LED and a flashing red firing LED while offering adjustable sensitivity for accurate testing.

Mechanics, technicians and DIYers need fast, reliable ways to verify ignition activity without cutting into spark plug wires. The Calterm Tru-Spark 66331 is a handheld tester built to detect secondary ignition voltage from DIS and conventional systems without piercing insulation. Rugged ABS construction makes it shop-ready while the sensitivity dial helps isolate individual wires in tightly routed harnesses.

How does the Tru-Spark show that an ignition circuit is firing?

The tool uses two LEDs: a steady green LED confirms the tester is powered and batteries are good, while a red LED flashes each time the coil discharges through the spark plug wire. You can watch the red flashes to confirm consistent firing events or intermittent misfires.

• Red LED indicates each ignition pulse visually.
• Green LED confirms tester power and battery condition.
• Non-contact sensing avoids damaging spark plug wires.
• Easy visual feedback for quick bench or roadside diagnostics.

Can the sensitivity be adjusted to prevent false readings?

Yes — Calterm included an exclusive sensitivity adjustment dial so you can tune the detector to the target wire and ignore nearby conductors. This is especially useful on engines where wires run close together or near metal that could cause stray coupling.

• Sensitivity dial isolates a single plug wire for accurate reading.
• Reduces cross-talk from adjacent wires in tight harnesses.
• Simple rotary control accessible on the tester housing.

Which ignition systems does the 66331 support and how durable is it?

The Tru-Spark works with both distributorless ignition systems (DIS) and traditional coil-and-distributor setups, making it versatile across many vehicle types. Its high-impact ABS housing resists oil, grease and the typical wear of a busy workshop so it holds up to everyday use.

• Compatible with DIS and conventional ignition systems.
• High-impact ABS case resists oil and shop abuse.
• Handheld and lightweight for portability during field troubleshooting.

How will this tool speed up diagnosis of a no-start or misfire?

By showing when and how often a coil fires, the Tru-Spark helps you quickly determine whether ignition energy reaches each plug wire. That lets you narrow the fault to coils, plug wires, spark plugs or other ignition components without time-consuming disassembly.

• Quickly verifies presence or absence of secondary voltage pulses.
• Non-invasive checks reduce the risk of creating new faults.
• Speeds troubleshooting, cutting down diagnostic time.

Who is this for: The Calterm 66331 Tru-Spark is designed for professional technicians, mobile mechanics and knowledgeable do-it-yourselfers who need a dependable, non-destructive way to confirm ignition pulses. It’s best for anyone working on passenger vehicles, light trucks or small engines that use conventional or DIS ignition systems and who value rugged build quality and adjustable sensitivity for accurate diagnosis.