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In this video, Mark Donovan of HomeAdditionPlus.com shows how to perform electrical wiring troubleshooting on unlabeled wires in electrical boxes.   Warning: Before doing any work on an electrical outlet, switch or fixture make sure to first turn electricity off to the circuit at the main circuit breaker panel, and then confirm that power is indeed off at the outlet or switch using a light circuit tester.   Often when do it yourself homeowners change a light switch or add a new light fixture or outlet they neglect to tape and label the wires inside the electrical box properly before removing the electrical switches, outlets and light fixture from the boxes.

Digital Volt Meters from Amazon.com

This can create a real problem when it comes to wiring up the new switch, outlet or light fixture. They end up not remembering where the electrical wires are going to and coming from in the electrical box.

To identify where the electrical wires are going to and coming from, a digital volt meter (DVM) comes in handy. By setting the DVM to a high resistance setting you can "buzz out" the Romex cable, or electrical wires, coming into the electrical box to see where they are going to or coming from.

To troubleshoot electrical wiring, connect two wires together associated with one Romex cable bundle in one of the electrical boxes, e.g. twist together the black and white wires coming from one Romex cable.

Then go to the next electrical box in the circuit where you think the Romex cable is going to. Place the two DVM probes on the respective wires of the far-end Romex cable to see if they show a short circuit, or effectively zero ohms reading on the DVM. If they do, then you have found the other end of the Romex cable. Tape and label the Romex cable on both ends and disconnect the short between the two wires that you had twisted together.

If the DVM does not register a short circuit, Zero Ohms, then check another Romex cable coming into the same electrical box or check another Romex cable coming into another electrical box. Eventually you will find the other end of the Romex cable that you had shorted together in the original electrical box.

With a DVM and this simple method you can effectively perform any type of electrical wiring troubleshooting. Again, just make sure power is off at the electrical circuit before working on it, and remove any temporary shorted wires after identifying and labeling the Romex cables. 

Related Information

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• Residential Electrical Wiring Tools Video
• How to Wire a Half Switched Outlet Video

- Electrical Wiring Troubleshooting Video  -

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