Topdon CT100 Circuit Tester
Topdon CT100 Circuit Tester
The Topdon CT100 is a battery-free automotive circuit tester built for technicians diagnosing electrical faults across cars, trucks, motorcycles and RVs. With a wide DC voltage range, integrated load testing and instant polarity protection, it delivers fast, dependable fault-finding on the workshop floor — without needing a separate power source.
- Wide DC voltage measurement from 3.3V to 65V with 0.1V resolution and high accuracy (±0.1V across 3.3–60V, ±0.2V from 60–65V)
- Built-in load test function (5–30V, 1.2A max) — hold the button for 5 seconds to check battery and circuit load capacity
- Clear backlit LCD with dual-colour polarity protection: red for positive, green for negative, plus on-screen ± indicators to prevent reverse connections
- Smart on-screen alerts for overvoltage (“H”), overheating (“Hot”) and lamp abnormality (“ER1”) to protect sensitive vehicle electronics
- Battery-free operation with a 12.5ft extra-long test cable and universal 4mm banana-plug connectors for interchangeable probes and clips
- Supplied with CT100 tester, 2mm probe, alligator clip, adapter, carrying bag and quick user guide
What Is the CT100 Used For?
The CT100 is designed for fast, practical electrical fault diagnosis in the workshop or on the road. Common applications include:
- Checking for voltage presence at fuses, relays, sensors and actuators
- Verifying earth continuity and identifying open circuits
- Load testing batteries, charging circuits and auxiliary power supplies
- Diagnosing blown fuses, failed bulbs and wiring faults across 12V and 24V systems
- Suitable for cars, vans, trucks, motorcycles and RVs
Technical Specifications
| Specification | Detail |
|---|---|
| Voltage range | 3.3V – 65V DC |
| Resolution | 0.1V |
| Accuracy | ±0.1V (3.3–60V) | ±0.2V (60–65V) |
| Load test range | 5–30V, max 1.2A |
| Cable length | 12.5ft (approx. 3.8m) |
| Connectors | Universal 4mm banana-plug |
| Power source | Battery-free (powered by vehicle circuit) |
| Display | Backlit LCD with dual-colour polarity indication |
| In the box | CT100 tester, 2mm probe, alligator clip, adapter, carrying bag, user guide |
UK-Based Support & Genuine Warranty Protection
When you buy from Dunns Automotive, you’re choosing the confidence of a genuine UK distributor. Every product comes with full UK warranty coverage and fast, reliable support from Topdon UK — no overseas delays, no grey imports, no uncertainty. Just authentic TOPDON UK tools backed by a dedicated UK team that’s here to help whenever you need it.