Circuit tester for professional automotive electrical diagnostics
2 June 2026 
TOPDON has introduced a new professional-grade circuit tester, the CT100, to offer workshops and mobile technicians a compact tool for fast, accurate electrical diagnostics across a wide range of vehicle systems.
Electrical faults are among the most time-consuming jobs an independent workshop faces, and vehicle electrical systems are not getting any simpler. Intermittent faults, voltage drops and weak connections that evade a basic continuity check can keep a vehicle on the ramp for hours, with knock-on effects for workshop throughput and the customer waiting for their car.
The CT100 is designed to solve these challenges without the cost or complexity of larger diagnostic platforms. Its built-in load bulb allows technicians to test circuit integrity under real operating conditions, replicating the electrical load a component would experience in use. This makes it possible to identify weak connections and voltage drops that only reveal themselves under load, faults that a standard test light or basic multimeter would not detect.
Voltage measurement covers a DC range of 3.3 to 65V with an accuracy of plus or minus 0.1V, making it suitable for both 12V and 24V vehicle architectures. A backlit digital display provides clear readings in workshop conditions, while dual-colour backlighting and on-screen indicators show positive and negative polarity at a glance, reducing the risk of reverse connections during testing.
Audible and visual alerts notify the technician of high-voltage conditions, overheating and reverse polarity in real time. A power-on tone confirms circuit continuity without requiring constant attention to the display, which is a practical consideration when working around vehicles in a busy bay. Standard 4mm banana jacks allow quick switching between the included alligator clip and 2mm probe, and the 3.8-metre cable provides enough reach to work around most vehicles without repositioning.
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