A short in an electrical wire will break the circuit and stop the flow of power to a particular outlet, or appliance. Shorts result from damage to electrical wiring. Such damage may occur at the factory, or the retail centre where the wires were purchased. A simple resistance test shows a wire's ability to carry current. Check the resistance in electrical cables before wiring anything in your home.
Set a multimeter to "AC Volts" for testing household electrical wiring at outlets. Set the voltage range to 120 volts, or slightly higher.
Test an electrical socket for a short in the wiring between a receptacle and the breaker. Touch the black lead of the multimeter to the rounded ground port, and the red lead to the hot port. The smaller of the two slotted ports is typically the hot port. Angle the leads so the points are touching the metal contacts inside the receptacle. Read the meter for voltage. The wiring has a short if zero volts register.
Test new electrical wires before installing them in the home. Set the multimeter for "Ohms." Zero out an analogue multimeter by touching the black and red leads together. Turn the calibrating dial until the needle on the reading display is on zero.
Touch one lead to one end of the wire. Force the lead into the open end of the insulation to contact the wire if there is no exposed wiring. Touch the other lead to the other end of the wire. Avoid skin contact with both leads.
Read the resistance value indicated by the meter. A positive number reading shows the wire is good. An infinite reading proves there is a short in the electrical wire creating an unlimited amount of resistance.
Longer wires show more resistance when tested for continuity on an ohm scale. Short lengths of quality wire will hold little resistance.
Tips and warnings
- Longer wires show more resistance when tested for continuity on an ohm scale. Short lengths of quality wire will hold little resistance.