How to Check Live Wires in a Wall Fixture

Check your circuit tester on a known power source before testing the live wires. The easiest way to do this is to hold one lead in each hand, gripping only the insulated handles. Do not touch the leads themselves. Put one lead into one side of a power outlet that is working and the other lead into the other side. Be sure they do not touch each other. The circuit tester’s light should come on or it should otherwise react -- some testers may use a sound or a gauge -- indicating the presence of power. If it does not, the tester is defective and should be replaced before you test the wires in question.

Expose the wires you want to test by removing the wall fixture’s cover plate. This is usually a matter of unscrewing one or more screws holding the cover to the wall. The number of screws may vary depending on the type of fixture. If the wires are already exposed, you can skip this step.

Place the exposed metal end of the black lead on the tester on ground. This can either be the place where the ground wire comes in or you can use the metal box surrounding the wires, which is normally grounded. The ground wire is typically white with no stripes or other colors on it.

Touch the exposed metal end of the red lead on the circuit tester to the end of the live wire, which is most often red but may also be black. In addition, sometimes a white wire will be used but should be wrapped in black electrical tape to show that it is not acting as ground but instead is being used to carry power.

Watch the circuit tester to see if it reacts in any way when both leads are touching the wires from the wall. If there is no reaction, the wires have no power to them. If the tester reacts, the wires are receiving power.