A test light is one of those simple electronic testers. This device determines the absence or presence of voltage in other equipments. The test light is composed of an electric lamp with one, or usually two, wire leads with insulation. Usually, the test leads have a screwdriver-form. The lamp connects between the screwdriver tips and a lead that sticks out at the “back-side” of the screwdriver. An operator connects the test light to a ground reference by touching the screwdriver tip to certain points in a circuit.  This detects the absence or presence of voltage in those points, as tracing faults to their main cause.

Using a test light is quite simple. The simplest way to do this is as follows:

  1. Get the ground clip connected with a ground source.  A battery’s negative terminal is the best ground source, but you may also use any grounded metal source.
  2. Connect the pointed (screwdriver) end of the apparatus to the circuit you want to test.
  3. The test light’s bulb will light up if power is present in the circuit. Informing you that the circuit you are testing is in good working condition.
  4. Test lights can also check circuit without disconnecting the system. Just press the pointed end of the apparatus to a wire with insulation.

Test lights are very good testers of voltage on circuit systems. But did you know that they are also capable of checking ground circuits? If you already know that the positive side of the circuit is getting good power, you must now check the status of the grounding point.

To check if the ground point is working properly, all you need to do is reverse the test light lead. To be more specific, these steps are all you need to do:

  1. Attach the ground wire of the test light to the positive side of a circuit.
  2. Now attach the other end of the test light to the ground source. If it lights up, you have a good grounding point.
  3. If it does not light up, you should clean the ground points to make sure that the power will flow without any obstructions.

Most car owners use test lights to check basic circuits on their cars. One such circuit is for their car’s radio wirings. Before doing anything, you should know which wires to test. Test light are able to set off supplemental restraints (airbags) in a car when you probe a wrong wire. These wires may be marked with yellow tape.

After you make the necessary precautions, checking your car system’s simple circuits is a snap. Test lights, when properly manipulated and used, become one of the best and most efficient simple devices to check 12-volt systems.

In this set-up, the test light will illuminate when the difference in power from the pointed end and the clip on the ground wire is sufficient. After checking this, let us assume that we are checking the circuit of a car’s radio. After installing the product into your car’s system, the test light will help you detect and troubleshoot if ever the radio does not operate. For specific calculations however, using a multimeter is best for this situation.

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