Finding the ground fault

My GFCI breaker intermittently won't reset. I think it is when there's been a lot of rain, but even when the rain has been gone for a week or more, it won't reset.

In 2006 JT2Fast4u said he has a multi-meter, and found a "neutral-to-ground" fault. But he never explained how he used the multi-meter to find the ground fault.

I know how to use the meter to see if there is 120V in the line, and if the GFCI would reset, I would have 120V in the line; but it won't reset. The breaker controls an outdoor lampost. How do you use the multi-meter to find the fault ? Is there a way to check for continuity between the GFCI and the outdoor outlet ?

 

Welcome to the forums.

In order to use an ohmmeter to check for a ground fault..... the wiring needs to be disconnected from the GFCI device. Remove the bulb from the post light.
Then you check from the white (neutral) line to ground and black (hot) line to ground. You should see no resistance at all.

This is how you check for a ground fault. It will not tell you where the fault is located. You could have an underground abrasion in your wiring in which it would need to be replaced.

 

Are there any receptacles outside that are connected to this circuit? Do they have "in Use" covers on them? Have you checked for corrosion at all connections at the light/photocell?

 

Thanks to both of you. You have both been of help. There is an outdoor outlet buried behind shrub, which may or may not be in line with the GFCI. I'm going to have to chop that shrub before I can get to the outlet and inspect it. It does have the "in use" covers Chandler asked about, but they don't guarantee an non corroded connection.
With regard to checking for the ground fault, it sounds like I can use the multi-meter to touch the center of the bulb receptacle to check the hot wire, and the base contact that the bulb actually screws into to check the white (neutral) wire. In other words, I don't have to disassemble the post to make this check, correct ?

 

I think PJMax means you should see infinite resistance during the checks...not no resistance at all (zero ohms).

 

No.....you don't have to dis-assemble the light post. You can check from the socket.
However, you still need to disconnect it from the GFCI device or source.

 

I was at a friend's house, debugging a GFCI outlet that just wouldn't stay on.

It turned out to be plants growing too close to, or in, an outdoor outlet wired as a protected extension to this internal one.

 

I decided to look at the wire connections of the actual light fixture. Once the light fixture was in my hands I could see small debris had collected inside the light sockets. Not enough to block any connections, but I decided to clean that out anyway. The debris was perhaps bits of insect parts or plant material or anything else. Next I disconnected the house wires from the wire leads leading to the fixture, brought the fixture into the garage where the GFCI is located, and connected the fixture directly to the GFCI. I reset the GFCI and the bulbs lit up without tripping the GFCI. So now I knew there was nothing wrong with the fixture itself. Before reassembling the fixture I used sandpaper to clean the ends of the wires. After reassembling the lamppost, the GFCI was willing to be reset. Was it the small bits of debris in the light socket, or just cleaner wire connections I will never know.
My advice to anyone having a GFCI that won't reset. Use your eyeballs to look for even the smallest thing that doesn't belong. Disconnect and reconnect everything you can, and maybe you too will get lucky.
Thanks to all of you who replied.

 

Thanks for posting the "fix". Good information.

 

Side note:
I personally don't recommend testing the socket. I had my journeyman blow up 3 of my friggin' flatblades trying to adjust the tab on the bottom of sockets.
If you do, have hands like a surgeon and make sure your leads don't touch the bottom tab and wall at the same time, or each other.