Locating break in electric cable

Old 02-05-17, 10:17 AM
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Locating break in electric cable

I am often called upon to help people with, for example, a vacuum cleaner which no longer works. First thing I do, I check continuity of the live and neutral wires between the plug and the machine. Most of the problems are just of a continuity nature along the 10-20 foot cable, but where? , Not always at the ends. Just cutting in the middle, and checking both ends for continuity, is pretty destructive.
Until now, I use a pin to pierce the wire covering and measure for continuity from there to one of the ends, and test the continuity until I find it, therefore not having to cut the cable unnecessarily. Works fine, but I don't like the fact that there are now a number of tiny holes in the wire covering. Is there any better method? I tried using a compass to see if there is only a swing in the live portion of the wire, butdoesn' seem to work.
Old 02-05-17, 10:25 AM
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If break is anyplace other than near plug I would replace the cord.
Old 02-05-17, 10:33 AM
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I would agree. Replacing the cord would be the easiest and safest way to make the repair.
Old 02-05-17, 08:37 PM
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Most of us on this forum follow North American codes and practices so what you do does not sit well with us. If you are in a location where people can't afford to replace cords you are in a tough spot. Pinholes promote air and water getting to the conductors shortening the life of the remaining cable. Hopefully you are finding a way to seal them afterwards.

I'm not sure but I think a regular compass is either not sensitive enough or only works with DC and a current flowing. Can you get a non-contact AC voltage tester? Lots of times that will help find a break in a cable as long as it is not metal covered.
Old 02-06-17, 03:11 AM
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Non contact tester will only detect a break in the hot wire, not the neutral. As all have said, replacing the cord is the best and cheapest solution in the long run. You can run up quite a labor bill attempting to find a break mid cord, when a replacement costs so little, and it is safer.
Old 02-06-17, 06:13 AM
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The only way I know of to non-destructively find a cable break is to use a time domain reflectometer (TDR). The problem with these for your application is that they have a minimum cable length of somewhere like 3-5 meters, and they can be quite expensive. For a couple hundred dollar price it can find the broken spot within +/- 1 meter roughly. For a price over a thousand dollars you can find a break down to the centimeter.
Old 02-06-17, 06:42 AM
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For repair work, you can "cheat". And that is a wire break with an appliance is most likely near the plug. People pull on the wire instead of the plug to remove it from an outlet.

I used to do "factory authorized service" and we would always replace the entire cord if it was bad.

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