I am wondering if there are any tricks electricians use before I start ripping walls to find a short. (Sigh).
I have isolated the short between the 2nd and 3rd light fixture in a hallway. The 2nd fixture is a recessed lighting box. The 3rd fixture mounts on a simple round wall box. There is no visible short in the accessible parts of the wire at the two ends. All three wires (hot, neutral, ground) are shorted together.
This is relatively new construction, finished about 1.5 years ago. The wire is standard 15A or 20A romex.
I tried measuring the resistance of the short from the two ends to see if I could tell where it is. My voltmeters measures down to 0.1 ohm which is a lot higher than a short length of romex. So I rigged a circuit with a 100W lightbulb to push about 1A through the short, and tried to measure the voltage drop from each side. This is tricky because a lot of the resistance is in the contacts and it varies a lot depending on how good they are. I was using alligator clips. The approximate readings are 220mV from the 3rd fixture and 200mV from the 2nd fixture.
Any tips/suggestions before I start breaking the wall near the 2nd fixture?
Thanks! Luigi