How to Test for an Open Circuit in a Home

Circuit breakers are located in the home's breaker box.
••• Jupiterimages/ Images

An open circuit is one that is discontinuous at a point preventing electricity from flowing through it. Although you can close and open a circuit at will using a switch, some open circuits may be caused by other reasons such as wire cut in the circuit or an accidentally blown fuse. You can test for an open circuit by testing the continuity of the circuit using a multimeter.

    Unscrew the main circuit breaker panel lid using the screw driver to expose all the wires and terminals for each circuit. Each circuit breaker is responsible for protecting a particular circuit assigned to it from power surges by tripping or breaking the flow of electricity. Use the wiring diagram to note labels on the terminals for all the wires on each circuit, showing where the ground, the hot and neutral wires connect.

    Turn off the power to the entire house before testing for open circuits. This serves as a safety precaution and allows the multimeter to work properly. Turn on the multimeter then set it to “Ohm” which is symbolized by the Greek alphabet omega. Set the knob to X1 on the multimeters if it has multi-testers under this setting. Touch the testing probe tips together to test if the multimeter is working properly. A good multimeter will read infinity or "OL" before the probes come in contact and zero after.

    Switch off the circuit breaker for the first circuit you are testing. Touch one test probe from the multimeter to the hot wire terminal on the circuit breaker that leads to the appliance in the house. Place the other probe on the respective neutral wire that leads back to the circuit breaker panel from the appliance. The multimeter will read infinity or "OL" if the circuit is broken or open, on the other hand, it will read zero if continuous.

    Maintain the first test probe at the hot wire terminal of the circuit. Remove the second probe from the neutral terminal then place it on the ground terminal for the circuit. Once more the multimeter will read "OL" or infinity if the circuit is open or zero if the circuit is functioning.

    Repeat Steps 3 and 4 for each circuit on each circuit breaker in the panel, making sure you test the ground as well.

    Things You'll Need

    • Multimeter
    • Screwdriver
    • Labeled house wiring diagram


    • Hot wires are red or black in color, neutral wires are white in color while grounds are either bare or green/yellow. Some multimeters have audio alerts and will beep as well as read "Zero" if the circuit is complete. Make sure any other switches on the circuit other than the one on the circuit breaker are switched on otherwise the multimeter might record a false reading.

Related Articles

How to Test Servo Motors
How to Test DC Motors
How to Read Amps on an Analog Multimeter
How to Check Three-Phase Voltage
How to Test a Diode Rectifier
How to Check if a Diode Is Bad
How to Test an Electrical Relay
How to Convert Watts to Volts
How to Diagnose a Circuit Board With a Bad Transistor
What Are the Applications of a Multimeter?
How to Use a Cen-Tech Digital Multimeter
How to Test an SCR With an Ohmmeter
How to Build a Buzzer for a Science Project
How to Troubleshoot With an Analog Multimeter
How it Works: Voltage Relay
How Does a 3-Pin Plug Work?
How to Check a Zener Diode
How to Test Resistors in a Circuit
How to Use a Resistor for 12 Volt to 5 Volt