Product Specifications for TOPDON CT100 Auto Circuit Tester
| BM Part #: | CT100 |
|---|---|
| Length: | 7.60" |
| Width: | 2.52" |
| Height: | 2.52" |
| Shipping Weight: | 0.75Lbs (12 oz) |
| Warranty: | 1 Year |
What's in the box:
- CT100 Circuit Tester
- 2mm Probe
- Alligator Clip
- Adapter
- Carrying Bag
- Quick User Guide
- Backlit LCD Display: Read DC voltage from 3.3 to 65V with 0.1V resolution — clear and precise, even in low-light conditions.
- Professional Load Testing: Hold the button for 5 seconds to apply a circuit load and identify weak connections, failing batteries, or voltage drops that a resting test would miss.
- Dual-Color Polarity Alerts: Red backlight for positive, green for negative — instant visual confirmation to help prevent accidental reverse connections and protect vehicle electronics.
- Battery-Free with Built-In Safety Alerts: Powers directly from the circuit being tested; displays overvoltage (H), overheating (Hot), and lamp fault (ER1) alerts for safer, worry-free use.
- 12.5 ft Oil-Resistant Cable: Extra-long coiled cable stretches to reach hard-to-access areas, with universal 4mm banana jack connections for quick swapping between the probe and alligator clip.
- Wide Vehicle Compatibility: Supports 12V, 24V, and 36V electrical systems — suitable for cars, trucks, RVs, and commercial vehicles.
Product Description
Chasing down an electrical gremlin in your car, truck, or RV doesn't have to be a headache. The TOPDON CT100 is a professional-grade automotive circuit tester that gives you a clear, accurate picture of what's happening in any circuit — fast. Whether you're a seasoned technician or a serious weekend mechanic, the CT100 cuts through the guesswork so you can get back to fixing vehicles instead of hunting for the problem.
Clear Readings Every Time
The CT100's backlit LCD display makes it easy to read voltage levels at a glance, even in dimly lit engine bays or under a vehicle. It measures DC voltage across a wide 3.3–65V range with 0.1V resolution, giving you precise readings rather than a vague "yes or no" from a basic test light. Accuracy runs within ±0.1V for voltages between 3.3 and 60V, and ±0.2V from 60 to 65V — reliable enough for professional diagnostic work.
Load Testing Built Right In
One of the CT100's standout features is its ability to perform a professional load test without any extra equipment. Simply hold the button for five seconds to apply a load to the circuit (DC 5–30V, 1.2A max), and you can quickly reveal issues that a resting voltage check alone would miss — aging batteries, weak connections, or voltage drops under load. This helps you confidently confirm whether a circuit is truly healthy or just masking a problem.
Know Your Polarity Before It Matters
The CT100 uses dual-color backlighting to alert you the instant the probe contacts a circuit. Red indicates a positive connection; green signals negative. On-screen + and – indicators reinforce this at a glance, so there's no second-guessing during testing. This built-in anti-reverse feedback helps protect sensitive vehicle electronics from accidental reverse connections — a simple safeguard that can save a costly repair down the road.
Safe Operation, No Batteries Required
The CT100 draws power directly from the circuit being tested, so there are no batteries to install, replace, or forget. Beyond keeping maintenance minimal, this design also supports a suite of safety features. The tester monitors for overvoltage conditions and displays an "H" alert, warns of overheating with a "Hot" indicator, and shows an "ER1" code if a lamp abnormality is detected. These real-time status signals keep you informed and protected throughout your diagnostic work.
Reach Where You Need To Go
A 12.5-foot oil-resistant coiled cable gives you the flexibility to reach circuits throughout the vehicle without having to reposition your ground connection or strain to fit into tight spaces. The CT100 uses a universal 4mm banana jack connection, and the kit includes interchangeable accessories so you can switch between a precision probe tip and an alligator clip depending on the test at hand.
Works Across a Wide Range of Vehicles
With a testing range that spans 3.3 to 65V, the CT100 is compatible with 12V, 24V, and 36V vehicle electrical systems. That means it's equally at home on passenger cars, light trucks, commercial vehicles, RVs, and more. Common uses include:
- Checking fuse integrity
- Verifying connector and terminal voltage
- Testing circuit continuity
- Tracing wiring faults
- Diagnosing starting and charging system issues
Frequently Asked Questions
What types of vehicles is the TOPDON CT100 compatible with?
A: The CT100 works with any vehicle that uses a 12V, 24V, or 36V DC electrical system. That includes passenger cars, light trucks, RVs, and commercial vehicles. Its 3.3–65V testing range also makes it a capable option for many non-automotive applications that fall within that voltage window.
What is load testing, and why would I use it?
A: Load testing checks how a battery or circuit performs when electrical demand is actually placed on it — not just at rest. A battery or connection might show a normal voltage reading when nothing is drawing power, but reveal a drop or failure the moment a load is applied. The CT100's built-in load test (hold the button for 5 seconds, DC 5–30V, 1.2A max) makes it easy to catch those hidden issues without additional equipment.
Does the CT100 require batteries to operate?
A: No. The CT100 draws its operating power directly from the circuit being tested, so there are no internal batteries to install or replace. This also helps keep the unit compact and maintenance-free.
What do the color alerts on the CT100 mean?
A: The dual-color backlight tells you the polarity of the circuit at a glance: red indicates a positive connection, and green indicates negative. On-screen + and – symbols confirm the same. Additional alerts include "H" for overvoltage, "Hot" for overheating, and "ER1" for a lamp abnormality — giving you a quick heads-up on any conditions that need attention.
Can I use the CT100 with different probe types?
A: Yes. The CT100 uses universal 4mm banana jack connections, so the included 2mm probe tip and alligator clip can be swapped out quickly depending on where and how you're testing. This makes it easy to adapt to different connectors, terminals, and test points throughout the vehicle.
