How to Find Electrical Wiring Inside a Wall

Switch on the cable detector and check the status of the batteries. Some detectors have a battery status light. Others will fail to bleep on start up if the batteries are dead. If the batteries need to be replaced, replace all of them at the same time.

Ensure that the power supply in the building is switched on if your cable detector can locate only live cables. Switch on an adjacent lamp or appliance to confirm that the power is on. Detectors that locate dead and live wires do not rely solely on magnetic fields created by electrical currents. To simply establish the existence of a wire, the status of the power supply is irrelevant.

Locate the obvious indications of electricity, such as outlets, wall lamps and switches. It is safe to assume that each is receiving power, so there must be wires leading to them. Look for the likely wiring routes between outlets, switches and lamps. For example, a switch that controls a lamp mounted a few feet higher up the wall is probably connected to it by a wire running directly between them. Starting your detecting in these areas increases the chances of quickly locating the main wiring routes.

Hold the detector with the detecting surface flush against the wall at any convenient location. For the sake of efficient searching, it's sensible to start either where you believe the wires to be or at one end of the wall so that you can work across it systematically. Slowly move the detector across the wall and wait for it to signal that it has located a wire. Methods vary, but most detectors will bleep or lights will flash. Mark the location on the wall. Trace the entire path of each wire and mark it on the wall as you progress. If the signal vanishes unexpectedly, move the detector in a circle around the last known position in case the wire has altered direction.