How to Test for Live Wire

Typical Neon Tester

Before addressing any electrical issue in your house -- changing an old light switch, for example, or replacing a plug socket that's not working -- always turn off the power at the circuit box. But even turning off the circuit breaker isn't in itself enough to ensure safety. Sometimes you've turned off the wrong circuit, or the circuit breaker is improperly wired and is allowing power through even when turned off. Use a simple neon tester to double-check that the power's really off before you start working.

Things You'll Need

• Neon circuit tester
• Screwdriver

Instructions

1. Each time you test whether an electrical circuit is live, first test your neon tester. If the tester has gone bad and fails to light up in the presence of an electrical current, it could give you a false belief that a circuit if off when, in fact, it's live. Test the tester on a wall plug-in socket that you know is live. Take one of the tester wires in each hand, keeping your fingers entirely on the insulated plastic part, and insert the two metal prongs into the two slots of the socket. It doesn't matter which prong goes in which hole. If the tester lights up, it works; if it doesn't, replace the tester.

2. To test a plug socket that you believe is turned off, repeat Step 1, pushing the two prongs into the holes. If the tester doesn't light up, proceed to unscrew the socket plate, then unscrew the socket from the electrical box and carefully pull it out of the wall so it's hanging from its wires. If it's an electrical switch, make sure that whatever fixture it controls doesn't turn on; if it controls a light, put a fresh bulb in to double-check that the socket is dead and that it's not just a burned-out bulb. Pull the light switch out of the wall in the same fashion as the socket.

3. Once the socket or switch is outside the wall, re-test the circuit from the point where the wires connect to the socket or switch. Touch one prong of the tester against the metal electrical box or copper grounding wire. Touch the other prong to each exposed wire, one after the other. If the tester lights up at any point, the circuit is live, and you should stop working on it immediately until it's turned off.

Tips & Warnings

• If you have children or pets, make sure they aren't roaming around the area where you've exposed the wires while you step away for any reason.

References

• How To Test Electrical Circuits.