Auto Circuit Tester w/ Load Test, LCD, Polarity Alerts

The CT100 is a professional automotive circuit tester built for speed, accuracy, and everyday reliability. It helps diagnose electrical issues quickly, identifies polarity, runs load tests, and provides clear audible and visual alerts to take the guesswork out of repairs.

Built rugged with a long oil-resistant cable and interchangeable probe and clip, it works on cars, trucks, RVs, and EVs. No complicated setup—just fast, precise results for pros and DIYers alike.

Professional Load Test

Unlike basic test lights, the CT100 features a professional load test function (DC 5–30V, 1.2A Max). Hold the button for 5 seconds to check battery and circuit load capacity, quickly identifying aging batteries, weak connections, and voltage drops for faster, more accurate repairs.

Precision Voltage Testing

Equipped with a clear backlit digital display, the CT100 measures DC voltage from 3.3–65V with 0.1V resolution (±0.1V accuracy from 3.3–60V; ±0.2V from 60–65V). With a wider range than standard testers, it delivers dependable performance for both professional technicians and serious DIY users.

Polarity Protection & Anti-Reverse

Dual-color backlighting (red for positive, green for negative) and on-screen ± indicators activate instantly when the probe contacts a circuit. This intuitive feedback helps prevent reverse connections and protects sensitive vehicle electronics during testing.

Safe, Battery-Free Operation

Battery-free operation eliminates maintenance and downtime while improving safety during testing. Integrated protections include overvoltage alerts, overheating warnings, and component status monitoring for dependable performance in daily automotive diagnostic work.

Intuitive Status Light Indicators

Color-coded backlight indicators confirm polarity instantly, while additional alerts display overvoltage (“H”), overheating (“Hot”), and lamp abnormality (“ER1”) status—keeping key operating conditions visible at a glance during testing.

Easy Operation & Extended Test Lead

The 12.5-foot extra-long test cable improves access to hard-to-reach areas without repositioning the tester. Universal 4mm banana jack connections support interchangeable probes and clips, enabling flexible testing across cars, trucks, RVs, and other vehicles.

Wide Vehicle Compatibility

With a 3.3–65V testing range, this versatile tester supports 12V, 24V, and 36V vehicle systems, making it ideal for cars, trucks, RVs, commercial vehicles, and more. Perfect for checking fuses, verifying connector voltage, testing circuit integrity, tracing wiring issues, and diagnosing starting-related electrical faults.