Topdon CT100 | Circuit tester
Warranty directly via AsTools
Warranty directly via AsTools
We handle warranty cases ourselves, quickly and without involving the manufacturer. Thanks to our own parts inventory and technical expertise, we can usually assist you immediately. Only in exceptional cases do we still send the product to the supplier.
2 years warranty on all products
2 years warranty on all products
All our products come with a 2-year factory warranty. This ensures you long-lasting quality and service.
Easy returns
Easy returns
You can easily request your return through your account. We will send you the return label by email. Return shipping costs are your responsibility.
Professional customer service
Professional customer service
Our experts are ready to help you quickly and professionally, both online and in our physical store. Questions? Feel free to contact us!
The Topdon CT100 is a circuit tester for diagnosing electrical faults in vehicles. The device features a bright digital display with backlight that shows DC voltage within a range of 3.3 to 65V, with a resolution of 0.1V. Additionally, the tester performs professional load testing up to 1.2A, which checks battery load and circuit load to identify worn batteries, poor connections, and voltage drops. Thanks to its wide measurement range, the tester is suitable for 12V, 24V, and 36V systems in cars, trucks, and motorhomes.
When connected to a circuit, the tester instantly displays polarity via dual-color backlight: red for positive and green for negative, supported by plus and minus symbols on the screen. The extended 3.8-meter test cable reaches hard-to-access locations without needing to move the tester. Via the universal 4 mm banana connectors, interchangeable probes and clamps can be used. The tester operates without a battery thanks to power from the circuit being tested, with built-in protection against overvoltage, overheating, and reverse polarity to safeguard sensitive vehicle electronics.
KEY FEATURES
THINGS TO NOTE
Application and functionality
The CT100 supports the following electrical testing functions:
- DC voltage measurement: Measures DC voltage from 3.3 to 65V with 0.1V resolution, for checking batteries, sensors, and power supplies.
- Load test: Draws up to 1.2A from the circuit to assess actual load capacity and reveal weak points.
- Polarity check: Displays instantly via red or green backlight whether a connection is positive or negative.
- Fuse test: Checks continuity and voltage on fuses without removing them from the fuse box.
- Wiring diagnosis: Traces breaks, short circuits, and voltage drops in vehicle wiring.
- Connector check: Verifies voltage on connectors and plugs when troubleshooting starting issues or intermittent faults.
What's in the box
- 1x Topdon CT100 circuit tester
- 1x 2 mm measurement probe
- 1x Alligator clip
- 1x Adapter
- 1x Carrying case
- 1x Quick start guide
Technical specifications
General
- The brand that manufactures the tester.Brand
- Topdon
- What type of device it is. A circuit tester checks current and earth; a wire tracer locates cables and short circuits.Type of tester
- Circuit tester with load
- The on-board voltage the tester can connect to. For testing lorries as well, 24 V or higher is required.Suitable for system voltage
- 12 to 36 V
- Where the tester draws its power from. Via the vehicle battery or circuit, there is no need to replace batteries.Power supply
- Via tested circuit
Measuring
- The voltage range in which the tester measures accurately. A wider range is useful for heavier vehicles.DC voltage measuring range
- 3.3 to 65 V
- The smallest voltage increment the tester can display. The smaller, the more precise the measurement.Voltage measuring resolution
- 0.1 V
Test functions
- The tester can supply current to components such as a motor or lamp, so you can see whether they work.Component activation
- No
- The tester helps locate the position of a short circuit or broken wire, saving considerable searching.Short circuit and wire break detection
- Yes
- Shows whether a connection is positive or negative.Polarity check
- Yes
Display and controls
- The tester gives a beep or tone, so you do not need to keep looking at the screen.Audible signal
- No
Protection
- Which faults the tester protects itself and the vehicle against. This prevents damage from incorrect connection.Protections
- Reverse polarity
- Overvoltage
- Overheating
Dimensions and weight
- The length of the test cable. A long cable also allows you to reach the rear of a vehicle.Cable length
- 3.8 m
- The temperatures at which you can use the tester, for instance in a cold workshop.Operating temperature
- -10 to 50 °C
- The temperatures at which you can safely store the tester.Storage temperature
- -20 to 70 °C
Other specifications
- Display
- Digital display with dual-color backlight
- Compatible With
- 12V, 24V and 36V systems
- Load Testing
- 5V to 30V, maximum 1.2A
- Measurement Accuracy
- 3.3V to 60V: ±0.1V · 60V to 65V: ±0.2V
- Polarity Indication
- Red light for positive, green for negative
- Probe Connection
- 4 mm banana plug
