Light post stopped working (broken wire?)

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Old 03-24-19, 08:26 AM
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Light post stopped working (broken wire?)

Over the winter my light post stopped working. The post is controlled by a single switch (4 switches in the box with neutrals tied). The post includes a GfI outlet and a photo sensor that goes to the light. The switch appears to be functioning correctly, showing 120v when switched on. The gfi outlet is first in the circuit, but the photo sensor/light are connected directly to the hot wires in the gfi (not on load). I unwired the gfi and had about 9mv on the inlet circuit. When my wife flipped it on, I had about 400mv. I'm trying to rule out a broken wire, but thats what I'm starting to assume.
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I don't think any other gfi's are tripped or other things in the circuit. No breakers tripped. The only change I've made is wiring up a Nest doorbell, but that's completely different circuit. There is a 3rd switch that we don't know what it does on the neighboring switch to the light post, but it doesn't affect voltage at the post when I flip it.

I have not unwired the switch yet to check for outdoor wire continuity, but I think that's the next step.
 
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Old 03-24-19, 09:13 AM
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Millivolts? It should be volts. How are you measuring and what with? Did you measure both hot to ground and hot to neutral?
 
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Old 03-24-19, 09:52 AM
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Reading millivolts is basically reading 0v.

Your next step is to disconnect the wiring at the switch and at the GFI receptacle.
Tie them together at one end and check for continuity at the other end.
 
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Old 03-24-19, 11:18 AM
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Measuring VAC with a fluke. I only mentioned mV because the slight jump when the switch is on, maybe lending itself to a broken connection.

I did only test to ground, not neutral. What difference would I be looking for when I test black to white?

I'll check continuity next.
 
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Old 03-24-19, 11:30 AM
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You can check for continuity between all three. You can check black to ground and white to ground.
From your description it sounds like you have an open hot wire.
 
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Old 03-24-19, 12:13 PM
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Ok. There's no continuity black to ground. I set the Fluke up outside clipped to the black and ground. Inside I touched the disconnected hot wire to ground and did not hear a beep.

I didn't disconnect all of the neutrals in the switch recepticle, since I would have to undo all 4 switches (and I'm against the clock on my toddler waking up). Do I need to disconnect the neutrals?

​​Any advice on how to find the break? I can get a locator and a cable break detector from work.
 
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Old 03-24-19, 12:40 PM
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You can leave the neutrals connected and as such.... you should measure a short at the light end between white and ground as the neutral and ground are combined at the panel.

If you don't get a short between white and ground..... you either have a completely open cable which is pretty rare or you have an undiscovered GFI device in the path as the GFI will open both the black and white lines.
 
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Old 05-17-19, 06:57 AM
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At the light post I hooked up my locator. The black wire wouldn't even locate out and hit the voltage limit on the transmitter. It was as if I wasn't hooked up to anything - meaning broken hot wire. The white wire traced back to my house just fine. I'll be digging next to my post and replacing the wire there. Will update what I find to round out the conclusion of this.
 
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Old 08-12-19, 11:49 AM
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Finally fixed it

I ended up fixing the problem.

I had forgotten my touchless AC detector which was key to getting to the bottom of this.

The problem was the 30 year old original splice about 5 feet from the house. I could see a white romex wire going into the ground that was under my siding. The AC detector showed this wire as hot. I started pulling on the wire to unearth it (while it was hot) and heard some popping. I found an ancient corroded splice in the ground that connected the white romex to the direct bury wire. I cut and spliced them back together with underground splice kit.

Yes none of this was safe. I was mad because I had just cracked the siding. Always only work with it deenergized.

The light works now. Thanks for the comments.


My first assumption at cutting the wire next to the post was wrong. I had to fix that with another splice.
 
 

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