HOW TOHow to Find a Hot Wire in the Wall

By Kevin McDermott

When you need to replace a switch or light fixture in an old house, it's often unclear which of the wires are live and which are neutral or ground wires. Modern electrical work is supposed to adhere to a standard set of color-codes--black wires are live, as are white wires with black tape on them, as well as red wires--but there's no way to know what shortcuts previous electricians may have taken with your system. It's important to get clear on that issue before you proceed with your wiring project

Instructions
Step1
Turn off all power to the room at the fusebox.
Step2
Remove the socket, switch or fixture at the electrical box in the room, by taking out the screws and disconnecting the wires. Spread all the wires outside the box, apart from each other.
Step3
Make sure no children are around, and warn any adults to stay away from the wires. Go to the fuse box and turn on the power.
Step4
Return to the electrical box. Taking care not to touch any wires with your hands, set one prong of the current tester against the bare end of the first wire, and the other prong against the metal of the electrical box. Note whether the light on the tester goes on. Repeat for each of the wires.
Step5
Turn the power off at the fusebox. Go back to the electrical box and wrap black electrician's tape around the length of any of the wires that lit up upon testing. Proceed with your wiring project.