Test light

A test light is used to check for voltage in an electrical circuit. It is in the shape of a screwdriver with a probe and a ground wire attached. There is a light bulb on the holder itself. When the clamp is placed on the ground and the probe touches the live connector, the bulb lights up. This indicates that voltage is available. If the bulb does not light, there is no voltage on the connector. They do not use a separate power source for their work but are powered from the measuring area.

A test light can be used to check for grounds by attaching the clip of the test light to the positive terminal of the battery or any 12-volt electrical terminal. The tip of the test light can then be used to touch the ground wire. If there is a ground connection, the test light will light.

Test lights have a limitation because they do not measure the magnitude of the voltage, but are only an indicator of the existence of voltage. However, this is enough for the technician when examining the correctness of the circuit in search of an interruption.

There are two types of test lights, a bulb, and an LED.

Test light with bulb

This is an older type of test light. The housing is made of transparent material and inside there is a light bulb (12V, 2W). When there is a voltage between the two probes, the bulb lights up. However, during the test, an unwanted supply voltage may be applied to the electronic device via the test lamp and may be damaged. Therefore, it is recommended to use another type of LED test light for testing on modern vehicles.