I went to reconnect my garage door opener this past weekend after having drywall installed, and realized there is an open/break in one of the conductors of the 2-wire that runs from the control panel by the house entrance and the opener above the door (jackshaft opener). I'm guessing I either stapled the wire too tight and broke it, or the drywall guys put a screw through it. Regardless, I'm curious if there is a way to locate the precise location of the break without cutting holes in the drywall and accessing the wire? Is there a tool that can detect the location of an open circuit? It may be cheaper to just fish a new wire, but it's a12' vaulted ceiling with no attic access and I don't really want to cut a bunch of holes in my brand new drywall. If I connected an AC voltage signal to the broken conductor, would I be able to detect the location of the open using a capacitively-coupled no-contact meter?

 

I just had a call where I found one of the sensor eye lines was shorted in the wall.
I abandoned it and stapled a new wire in place. It's only a garage.

You could probably use a fox and hound tracer to locate the open but it will be easier to just abandon the line.

 

I'll probably just cut holes and fish a new wire or just mount the panel by the garage door.

 

My customer was adamant that it couldn't be a shorted wire as it had worked for 15 years.... but it was shorted. I couldn't explain it and it would be almost impossible to find without opening the rock.

 

here is a "cheap" TDR:

https://www.picotest.com/measurements/MeasuringPCB.html

 

Telecom guy, I doubt many DIYs have an oscilliscope in their toolbox. The TDR by itself does not tell you anything.

 

I actually carry a handheld TDR but wouldn't even break it out for a job like this.

 

It won’t be long when they will work with a smart phone.

 

Most Android phones now come with a FM tuner chip.

I VAGUELY remember my computer-engineer-Dad tracking down a break in an undergound wire to an outside light post by flipping the breaker, jumpering the hot wire to the distributor cap of a running car, then using a transistor radio to track down the signal.

 

Distributor cap?
Transistor radio?

Yeah, that was a while ago.

 

<quote>Distributor cap?
Transistor radio?
Yeah, that was a while ago.
</quote>

At least is was a BREAKER, not a fuse....

The point is, if you can put a FM signal onto a broken wire, a modern android phone should be able to pickup that FM signal.

It should ALSO be possible to do something similar with a WiFI signal, especially since there are so many "WiFi signal strength" apps out there.

 

Last summer I bought a

Noyafa NF-816-C Underground Cable Wire Locator Locate Pet Fence Wires, Metal Pipes, Electrical Wires, Telephone Wire, Coax Cable with Earphone

on Amazon for $39 and was able to find a buried valve box in my irrigation system. According to the instructions you can also use it to find breaks in electrical wires behind walls.

 

I actually have a working analog Tektronix 2230 oscilloscope.

Injecting and AC signal on the broken wire and sniffing out the electric field with a no-contact meter isn't viable?

 

This is small zip cord, correct? and, only one side has the deficit/break?
I suspect the no-contact sensor will not detect a normal 60Hz signal over an inch away. I have problems with them when trying to detect a line voltage outside a TR receptacle. Maybe my G-B unit is not very sensitive.

Could be a AM transistor radio has merit with noise injected on the one wire. I have heard that using a small voltage source with a wire end running along a file makes a hellatious signal on an AM radio.

 

You could try using a Fox and Hound type tracer. You'd need to short the wires at one end and inject on the other two wires. I have found open alarm wires this way.

 

Small gauge solid copper 2-wire with only one conductor having a break in it. The wire is just on the other side of the sheetrock, about 1-1/2".

Would this tool work? A Youtube video showing its operation implies it would: https://www.amazon.com/gp/product/B0...k_ql_qh_dp_hza

 

I spoke with a couple guys at work and they made a good point...the tone would couple into the second wire and make it nearly impossible to detect the break in the other wire. Unless maybe I ground the second conductor?

 

Yeah, I was thinking the same thing. Also, are the drywall screw heads still exposed? You could consider using needle DMM probes and see if a screw head has continuity to either wire. Is this steel stud or wood stud wall?

 

No. It is all finished and painted. Wire runs through the ceiling (trusses with no attic access).

I did a little experiment (found a meter at work) and I may have found a configuration that could work. I laid out a 6' length of 2 conductor wire on the table, connected the red lead to the broken wire, connected the other three ends of the wires together and to the black lead and found that the tone gets nearly silent where the open is. Think I'll take the meter home and try it out.

 

It worked! I was skeptical at first, but identified a spot to where the amplitude of the tone decreased significantly, cut a 6" hole in the sheetrock, and located the section of wire with the severed conductor. Patched the wire and all is good now

 

For anyone curious as to why it worked, the source signal fed into the wire is an AM signal. When I twisted the opposite ends together the source signal travels back towards the source on the parallel conductor 180 degrees out of phase, which doubles the amplitude of the AM signal and thus doubles the signal picked up by the receiver probe. This is why the tone is so much louder along that section of wire then gets half as loud from where the wire break is up to the source. Not sure I explained that clearly, but for those of you that understand RF, it should make sense.

https://www.mediafire.com/view/lm0ed...racer.jpg/file