All legs of a lighting circuit down, but 120 volts off my breaker

Question

I'm not an electrician, but usually a capable homeowner for troubleshooting my own electrical issues.

My issue is that I have a 15amp lighting circuit where all legs are currently down. Started a few days ago. I have a bunch of Lutron Caseta switches on these legs and figured maybe they all got fried with a surge or something..

So, I pulled one of the switches off in my dining room and touched my line and load wires together expecting to see my lights come on. They did not.

Since all legs are down, my next thought was the breaker went bad. It happens. Replaced the breaker. No lights.

Next I broke out the multimeter. Measured directly off my breaker and I have 120v. Put the old breaker back in and the same thing. 120v off the breaker.

Went back to the exposed switch and got a baffling 10-60v. Some quick searching, I read that digital meters can sometimes read "ghost voltage" and only work reliably when there is load. Not sure if this is true, but I turned the breaker off and measured 0v. So it seemed like something was coming through based on the breaker being on.

Perhaps that test doesn't prove anything (I don't know), but this issue is now past my homeowner range of knowledge.

Any ideas of what is going on? What else could cause all legs of my circuit to be down when I'm getting 120v off the breaker? This just started a few days ago and there has been no electrical work of any kind in months/years.

Answer 1

First, let me address the ghost voltage bit. Yes, it is true that ghost voltage shows up on most digital meters. It is caused by capacitive coupling across two or more legs when at least one of them is energized. If you do a lot of DIY work, it is very much worth picking up a Fluke 117 which is capable of reading over the ghost voltage. If you're interested in learning more about the physics side of electricity, check out Veritasium's YouTube Video The Big Misconception About Electricity.

Up until recently, most homes with dedicated lighting legs had them wired in series to save cable. If your home is wired in series then you're probably looking at a loose neutral in the first box.

This would cause all lights past that point to have no power. Your best bet is to identify all boxes that are powered by that breaker and check the wiring to ensure there aren't any faulty connections. If you can't find the issue using that method, you're going to have to manually trace each cable and find the broken circuit.