TOPDON CT100 Automotive Circuit Tester Supports 3.3-65V DC
The CT100 is a professional automotive circuit tester built for speed and accuracy. It helps diagnose electrical issues, identifies polarity, and provides clear alerts. Built rugged with a long cable and interchangeable probe, it works on various vehicles. Fast, precise results for pros and DIYers.
The built-in professional load test function supports DC 5–30V circuits with up to 1.2A output and activates with a simple press-and-hold operation. It monitors real-time voltage drop to help identify weak batteries, poor connections, and internal circuit faults—enabling fast, accurate, and reliable diagnostics for automotive electrical systems.
The CT100 measures 3.3–65V DC with dependable accuracy across a broad range of automotive electrical systems. It delivers ±0.1V accuracy from 3.3–60V and ±0.2V accuracy from 60–65V, helping technicians diagnose circuits, batteries, and electrical components with greater confidence.
The CT100 automatically detects positive and negative polarity using color-coded backlight indicators(red for positive connection, green for reverse connection) and clear ± symbols on the display. This instant visual confirmation helps prevent reverse connections and protects sensitive vehicle electronics during testing.
The high-contrast digital display shows real-time voltage and polarity clearly. The 0.1V resolution readout delivers direct, accurate data at a glance for fast, intuitive diagnosis.
Distinct audible alerts indicate startup status, reverse connection warnings, active load testing, and overvoltage or overheating conditions—allowing technicians to monitor circuit status without checking the display.
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.
The CT100 is compact, lightweight and easy to carry for everyday diagnostics. The 12.5-foot extended test lead gives you greater reach without constantly repositioning, while universal 4 mm banana plugs support DIY accessories and compatibility with most standard probes and clips.
Tackle diverse testing and diagnostic jobs with one professional tool.
DIY Automotive Enthusiasts
Vehicle electrical system testing, battery condition checks, circuit troubleshooting, and basic wiring diagnostics
Auto Repair Shops
Daily electrical inspections, load testing, fault detection, and routine vehicle maintenance support
Technical Training & Education
Circuit principle demonstrations, polarity identification training, voltage measurement practice, and hands-on learning
Professional Automotive Technicians
On-site vehicle fault diagnosis, fleet system maintenance, electrical verification, and in-depth circuit analysis