Short Circuits

One telltale sign of a short circuit is black, smoky residue on switch or receptacle cover plates. Frayed or damaged cords and plugs also can be sources of short circuits. You need to check further for the source of the problem if your circuit goes dead and …

➤ You cannot find any visible signs of an electrical short.
➤ The circuit is not overloaded.

Before replacing the fuse or resetting the breaker, turn off all the loads and unplug everything from the receptacles. If the new fuse blows or the breaker trips right away, your problem is either in one of the devices (a switch or a receptacle) or in the wiring itself. To make sure the current is dead, remove all the cover plates and examine each device for charred wires or black residue. Clip the ends of any affected wires, strip off sufficient insulation, and install a new device. Replace the fuse or reset the breaker, and test the circuit again.
What if the circuit doesn’t short immediately after you set the breaker or replace the fuse? In that case, activate each load one at a time and then turn each one off. Check the load that eventually causes the short. The problem will be either in the fixture or appliance itself or in its wiring. Replace the offender and check the circuit again. If it still shorts out, you have a problem in the wiring itself and should call an electrician. Shorts in the wire almost always are at the device or fixture box, so the problem should be visible when you do your own inspection. Sometimes, however, the problem is caused by a splice or junction box buried in the wall and is therefore unnoticed upon first inspection. In the case of a plug-in appliance or lamp, if the circuit goes dead as soon as you insert the plug, you can assume the short is in the cord or the plug (both of which can easily be replaced). If the short doesn’t occur until after the appliance is turned on, the problem isn’t in the cord or the plug but in the appliance itself. You should then repair or replace the appliance.