I ran a wire from the garage to the corner post of a vinyl fence and made an internal splice in the post. I spliced it to another 12-2 wire that runs underground about 60' to a flower garden.
I have a switch in the garage with power off of a GFCI receptacle. Flip the switch and the GFCI trips.
I have isolated it from the power. Testing the white and ground with a continuity I have continuity. I know I have a short. Weather, back surgery and a mud spot by the post have stopped me from checking the splice in the post.

What tool is necessary to locate a problem in the ground (hopefully its in the post splice)? Really wanted to know when I test continuity on the black and ground I get a slight movement with the needle.

  • 1
    since you are unable or unwilling to check your work (at the splice point) there is not much it can be done.
    – asinine
    Dec 1, 2022 at 1:27
  • 8
    You have neatly indicated why your code-violation inaccessible splice inside the post, rather than in a permanently accessible junction box, is a code violation. Or possibly why the wise choice is conduit, not direct burial cable. With conduit, you never have to dig the same trench twice.
    – Ecnerwal
    Dec 1, 2022 at 2:03
  • 2
    Is all the wire UGF? Or is the second run made out of NMB (yellow or sometimes white)? NM outdoors, the insulation rots and starts tripping GFCIs. Dec 1, 2022 at 6:42

2 Answers 2


There is no trick. Just check the parts you can access. Once you have eliminated those, you will have to dig it up


Technically there is a a device called a Time Domain Reflectometer or TDR that can be used to locate the distance of a fault in cables. In practical terms, they are expensive, relatively difficult to use, and require calibration to the specific cable type, so it's not really an option. You can't do this with your basic meter or really any other common test equipment.

What you can do is check the accessible parts. If they're all good, time to get the shovel out.

  • I was going to post something similar. One minor point though. A TDR really doesn't have to be calibrated for the specific cable type if all you're looking for is opens and shorts.
    – SteveSh
    Dec 1, 2022 at 1:36
  • And you can gin up a poor man's TDR with a good oscilloscope and a fast pulse generator. How good a 'scope & pulse generator depends on what kind of distance resolution you need in locating the fault.
    – SteveSh
    Dec 1, 2022 at 1:38
  • 4
    If you want to know where the opens and shorts are, the TDR needs to be calibrated to the cable. Just open and shorts with no idea where they are can be done with a multimeter, and apparently already has been, in this case.
    – Ecnerwal
    Dec 1, 2022 at 2:08
  • ^- that. Finding a short and a vague idea of distance, sure, doable without calibration. Getting it down to the meter requires both calibration to your cable and knowing that it doesn't have water intrusion.
    – KMJ
    Dec 1, 2022 at 5:42
  • In power systems, there's a separate device called a thumper. It generates a high voltage pulse that creates an arc and an acoustic thump at the point of failure. The thump is detected either by simply listening or using a sensitive microphone that's stuck into the ground. This method avoids calibration issues in TDR/TDT.
    – user71659
    Dec 1, 2022 at 21:15

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