# Extension Cord Testing



## Tony Wells (Sep 3, 2016)

OK smart guys, I need some ideas. I have a couple, but want to see what the group comes up with.

I have a nice, 100 foot long 12-3 conductor extension cord, with a triple tap on the female end. Somewhere in the cable, there is an open in either the neutral or hot conductor, making it useless in the current condition. It's probably near one end or the other, but they are molded and not readily accessible to test. What I am trying to determine is a way to determine where the break is. I don't mind losing some length on the cable, but I am loathe to just whack the ends off and replace the connectors just to see. Especially the triple tap. If I have to, I will put a new male end on, but would rather find out where the break is and fix just that end, if it happens to be near to the end. I may end up losing the triple anyway, but if that's the case, I'll just live with it. Got it free with some other stuff at a garage sale years ago, and just set it aside for the time. I know I can check between the gnd and both the hot and the neutral to see which one it is, but as far as how far down the cable, or which end it is closest to....I can't seem to figure a sure way. Not that I really need it, but I hate having stuff that doesn't work.

Any ideas?


----------



## gr8legs (Sep 4, 2016)

95% of bad extension cords are bad at one end or the other - so the first test is to plug the cord into a known good outlet and plug a test lamp into the outlet end. Then vigorously flex the cable at each end and see if flexing either end gets the lamp to flash. If it does then you know which end to replace.  This may also work for a break in the middle of the cord but takes much longer to locate because you have to massage every 3" section of the cord. 

If that doesn't work then get a non-contact voltage sensor and run it from the source end along to the output end until it goes dark. Note that this only works if the break is in the hot lead (you can determine which lead is bad with an ohmmeter), and also note that the conductors in extension cords are spiraled around at about a 5" twist so the tester will flash as you move along the cord.

I have occasionally used a capacitance meter to determine the length of contiguous conductors but the method isn't all that reliable. 
 Also, if the break is mid-cable then the cord has probably been over-stressed either mechanically or electrically and another failure should be expected. 

Good luck!

Stu


----------



## RJSakowski (Sep 4, 2016)

If you can't find the open at one of the connections, you can always cut the cord in half.  One half will be good.  Wire a new plug or socket and you're good to go.  You can cut the remaining length in half and wire the good half  with new connections.  You will have 75 ft. of good cord.


----------



## RJSakowski (Sep 4, 2016)

gr8legs said:


> If that doesn't work then get a non-contact voltage sensor and run it from the source end along to the output end until it goes dark. Note that this only works if the break is in the hot lead (you can determine which lead is bad with an ohmmeter), and also note that the conductors in extension cords are spiraled around at about a 5" twist so the tester will flash as you move along the cord.
> 
> Stu


If the break is in the neutral lead, you could temporarily jumper a hot wire to the neutral.  The easiest way to do this is to use a duplex outlet and cross wire a power cable to it.


----------



## Tony Wells (Sep 4, 2016)

Stu, pretty much done that with the shake test for each end, but have not massaged all 100 feet of it. No indication of a break near the ends, as I had hoped.

Also tried the ticker. Even went to 240 volts, since it seemed to be sort of hit or miss along the wire. Not much difference. And yes, knew about the spiral wind in the cord.

One promising idea I had does involve a Z meter. Being as there are 3 supposedly equal length wires in this cable, and they are twisted, they should make some sort of "gimmick" capacitor. The pair with the lowest measured capacitance would include the broken wire. I just am not convinced that there will be a measurable difference if the broken conductor is, for instance, only about 10 feet shorter than the others. If that is the case, however, and I identify a "bad pair", I can check from the other end and the measured value should be substantially lower. Ruling out the wires with lack of continuity is the easy part. I know which one is broken, I just need to know how long each "half" is. In the low voltage world, there are instruments that are designed to locate breaks in network wiring. My brother has an instrument that we use to certify the LAN cabling we run. It gives a length value for each of the 8 conductors in CAT 5 cabling, for example. I'm not positive how it does this, but I believe it bounces a pulse off the end of the conductor and times the return, sort of like radar and sonar. It's amazing how much difference there can be between the 8 conductors over a run of say, 800 feet. And of course, that can be detrimental to traffic over the cable. But I digress. I am thinking that I may get it and check this cord using one of the known conductors and the short one to see how short the machine see it as. I can do this from both ends and see if it all adds up close to the supposed 100 feet. It won't. Even the good conductor will be long, because of the twists, but if one is broken, it should show up as really short. (I hope)

As far as mechanical stress, this cord looks almost new. There is no damage to the jacket that I have found. I have a feeling the break is near the end, but this is also an educational opportunity.

RJ, Yeah, I thought about that too. It may come to that if I can't resolve this wire break issue. Really rather not have to do that. But I will rather than toss it.
It's been a little while since I stretched it out to work on it, but if memory serves, it's the hot that broken, but good point on temp criss-cross wiring on the neutral and the hot.

Good thinking, guys......keep em coming!


----------



## cvairwerks (Sep 4, 2016)

TDR....Time Domian Reflectometer. We use them to check coax on the airplane when we have problems. Not a cheap instrument at all, and it take some skill to read and interpret the display results.

New 12/3 triples are around 59$ at Amazon, so value your troubleshooting time as appropriate.


----------



## Tony Wells (Sep 4, 2016)

Oh, I know......but like I said, this is partly a mental exercise and I like a challenge. And it's not the only 100 footer I have. I have 2 or 3 10-3 cords too, but they are home made with a quad box on one end. Versatile and heavy for when they are needed. This is mostly stubbornness lol.

I could always juice it up with a few KV or so and wire up one end shorted, then see if the arc that jumped would blow a hole in the insulation.

Speaking about coax.......I may have a tester that does measure coax length. Not often used, but I may have to dig it out and play with it.


----------



## juiceclone (Sep 4, 2016)

The non contact volt sensor will work as described above.  Get one of those old adapters that lets u plug in either way to test the neutral side.  The triple taps, particularly the crowfoot type, are notorious for failing inside the molded rubber body .... possibly bad design or quality...or maybe just an abused life .?


----------



## John Hasler (Sep 4, 2016)

Tony Wells said:


> My brother has an instrument that we use to certify the LAN cabling we run. It gives a length value for each of the 8 conductors in CAT 5 cabling, for example. I'm not positive how it does this, but I believe it bounces a pulse off the end of the conductor and times the return, sort of like radar and sonar. It's amazing how much difference there can be between the 8 conductors over a run of say, 800 feet. And of course, that can be detrimental to traffic over the cable. But I digress. I am thinking that I may get it and check this cord using one of the known conductors and the short one to see how short the machine see it as. I can do this from both ends and see if it all adds up close to the supposed 100 feet. It won't. Even the good conductor will be long, because of the twists, but if one is broken, it should show up as really short. (I hope)



The cord may be so lossy at those frequencies that the tester can't get enough signal back to get a measurement, but it's worth a try.

The tester will be way off as to actual length, but you just need relative measurements.  Use it to measure the good pair and write down whatever it claims the length is.  Then measure the bad pair and figure out the distance to the break as a percentage.  Measure from both ends and average the results.


----------



## Tony Wells (Sep 4, 2016)

Juice, the ground is fine. I have continuity on it and the hot. The neutral is broken, I just don't know where, exactly. The sniffer/ticker is apparently sensitive enough, and there is inductive coupling in the cable so that it picks up all the way, so that method is out. It doesn't matter which end I apply power to for the test, so apparently both connectors, including the crow's foot triple are ok. 

John, yes, I realize there is no real comparison between an extension cord and CAT wiring . I am just hoping to find something that works. I don't know what frequency, or profile the tester uses, but it tests a little above CAT 6 for speed certification. It's one of those little Byte Brothers certifiers. I know it's not going to read correct on really anything, but I am relying on difference in what it "thinks" it sees. Just for curiosity, I may hook it up to a scope and or frequency counter to see what kind of signal is uses. I have noticed one odd thing about it after using it for a few years. A short cable, like a patch cable, takes a LOT longer to cert that say, a thousand foot run. Seems it runs many more iterations for the speed test, or delay, skew....who knows why. And there are different settings for solid vs stranded. None of that should matter for my needs though.


----------



## jim18655 (Sep 4, 2016)

Plug a lamp into the cord and the non-contact tester will light on the open neutral conductor. You'll have to start at the triple connector end and go back toward the plug end. You could use a jumper and power just the neutral with voltage and trace along the cord until it stops.


----------



## chips&more (Sep 4, 2016)

Try sticking a small diameter sewing needle into the cord. Your aim will need to be intuitive. But I think you will hit the selected wire especially when near the cord ends. Then check for ohms. Your problem is more than likely at or near the ends so you can guesstimate where the wires are within the cord…Good Luck, Dave.


----------



## Tony Wells (Sep 4, 2016)

Jim, already tried just powering the neutral, and I am guessing the inductive coupling in the cord is acting like a transformer in a way, because even the hot sniffs current when I do that. I need a less sensitive sniffer. Maybe using a signal generator I can find a frequency that doesn't couple and use my frequency counter with a pickup loop where I can control sensitivity by moving a bit away from the cord.

I never thought about having to do this, now I am becoming obsessed with how to lol......must be the OCD in me coming out.


And no, I'm not going to make a pincushion out of a good cord (well, hope to make it a good cord) The way I use mine, it's liable to be laying in puddles and who knows, so I can't risk violating the integrity of the jacket.


----------



## jim18655 (Sep 4, 2016)

Do you have a variac transformer? You could turn the voltage down. Some of the tracers go down to about 50 volts. Also ground the conductors you aren't using to drain the induced voltage away.


----------



## Tony Wells (Sep 4, 2016)

Jim, I have several Variacs as well as a Tenma isolation transformer (variable voltage) on the bench. I hadn't thought of grounding the conductors not under test to eliminate the induced current, that should help. I don't have one of the low voltage sniffers. I know they make then for <50 VAC or so. Mine is the regular line voltage rated one.


----------



## John Hasler (Sep 4, 2016)

Tony Wells said:


> Jim, I have several Variacs as well as a Tenma isolation transformer (variable voltage) on the bench. I hadn't thought of grounding the conductors not under test to eliminate the induced current, that should help. I don't have one of the low voltage sniffers. I know they make then for <50 VAC or so. Mine is the regular line voltage rated one.


Also ground the far end of the defective conductor.  Just short all three conductors together at the far end.


----------



## dlane (Sep 4, 2016)

Bet it's the triple tap on the female end, I've had a couple go bad just from dropping them.


----------



## RJSakowski (Sep 4, 2016)

Some time ago, I used thousand foot spools of Belden three conductor cable.  I had a length that had an open conductor fresh off the spool.  

We had an electric fencer running in the back yard and I connected one end of the bad conductor to the fencer and the other end to ground.  I then worked my way down the cable listening for the spark jumping the gap.  I was able to locate the break and on opening the cable up , discovered that it was a factory splice, hand twisted with a bit of insulating wrap around the splice.  Apparently pulling on the cable had stretched it enough to separate the wires.


----------



## TOOLMASTER (Sep 4, 2016)

with a jumper wire liven one wire at a time and check with non contact tester


----------



## Tony Wells (Sep 4, 2016)

RJ, you may be onto something. I can short all three conductors together on one end and grab an old power transformer from some of my old tube gear and use the plate voltage to arc this open spot. Wherever it is, I don't care if it burns the jacket, it's getting cut there anyway.

Toolmaster, we have discussed that option and having tried it, it doesn't help. But we have brought up some variations that may. So I will have a few different things to try when I drag it back out.


----------



## TOOLMASTER (Sep 4, 2016)

did you only liven one conductor at a time?
an ohm gauge will tell you which wire is dead..liven that wire only and you will see where the power stops





Tony Wells said:


> RJ, you may be onto something. I can short all three conductors together on one end and grab an old power transformer from some of my old tube gear and use the plate voltage to arc this open spot. Wherever it is, I don't care if it burns the jacket, it's getting cut there anyway.
> 
> Toolmaster, we have discussed that option and having tried it, it doesn't help. But we have brought up some variations that may. So I will have a few different things to try when I drag it back out.


----------



## Tony Wells (Sep 4, 2016)

Yes sir, tried live at 127 VAC, and at 245 VAC. Problem was that the adjacent conductors picked up current inductively and also read as live. So now I will ground the ones not being tested. Or, thinking about it, looping them back and connecting the ends should kill any inductive effect.....correct? So then, the only possible live one would be the open conductor if I am thinking correctly.

Derrick, you're probably right. I'll end up just chopping the triple off and putting a quad box on it. I just don't like the bulkiness of that, although I have a cord or two like that. But this is an exercise, for one thing, to see how many ways there are to find a hidden open in a multi conductor cable.


----------



## TOOLMASTER (Sep 4, 2016)

then send it in on the other end


----------



## TOOLMASTER (Sep 4, 2016)

some testers are very/too sensitive


----------



## Tony Wells (Sep 4, 2016)

Oh, I've tried it from both ends, and every combination I can think of. So, I'm all in for some entirely different methods. I used to have an underground pipe locator, but I loaned out and it didn't come back. I can borrow one, but I'm not sure that's the answer yet either. I have a few ideas to try now. Will be a day or two. Labor day is tied up with honeydo's and plenty of other stuff, but I'll get this done.


----------



## TOOLMASTER (Sep 4, 2016)

do you have an open showing with a ohm meter?

end to end then the 3 on one end


----------



## TOOLMASTER (Sep 4, 2016)

maybe you can get a new one if it is recalled ;-)



http://search.cpsc.gov/search?site=...sheet=CPSC_frontend&filter=0&q=extension cord


----------



## FOMOGO (Sep 4, 2016)

I think I would go the divining rod route. Casting my vote with the with the bad 3-way end crowd. Mike


----------



## Tony Wells (Sep 4, 2016)

Yes, the neutral is open with a meter, on all three on the triple tap end, so of course it is the most suspicious end. Recall? Doubt I would qualify, being I got it free from a garage sale when I bought some other stuff.

We'll see what the divining rod says. I can wind a coil for an antenna and send a known frequency RF down the line. Surely it will drop off in strength where the break is. I will run the cord through the loop.....all 100 feet of it.


----------



## TOOLMASTER (Sep 4, 2016)

if you run hot to the triple end neutral and it is open at that end you should not get any cross contamination


----------



## cvairwerks (Sep 5, 2016)

By the time Tony gets his satisfaction with this cable, he better put it in a good safe, as it will be worth it's weight in platinum.


----------



## vhol5 (Sep 5, 2016)

I have found that if you grab the end of the non contact tester with two fingers as you're testing, the sensitivity is greatly reduced.


----------



## Dave Smith (Sep 6, 2016)

Tony---OK---I guess I better give my solution after knowing the frustration of a bad cord------first the triple female end is always a problem since it is all encased and not fixable---just cut it off and a couple inches of the cord----then recheck the remaining three wires with the ohm meter to be sure they are still good---now install a new good quality single female end and your job is done---except find one of your spare six outlet switched with breaker power strips  and keep it with your cord in case you need multiple power at times---that way you don't have to have a heavy multiple box on the end of your cord---Dave


----------



## Tony Wells (Sep 6, 2016)

Oh, it's not that so much Dave. I have plenty of cords. It's figuring out a solid way to test it. I agree that it is likely the triple tap end, but now it's the principle of the thing. I don't want to just hack off the end, even knowing the odds are that the problem is very likely there.


----------



## TOOLMASTER (Sep 6, 2016)

hook it up to a coil   listen for the spark


----------



## Tony Wells (Sep 6, 2016)

Toolmaster, see post 20 

Might use a ballast from a fluorescent fixture. The old ones run about 970 OCV. Feels good. If they'll make a Jacob's Ladder, they ought to do this.


----------



## TOOLMASTER (Sep 6, 2016)

just don't grab it when its on...it tickles


----------



## Tony Wells (Sep 6, 2016)

I'll wait until it's raining and throw it out the overhead, and hook it up inside. Might be worth recording.


----------



## Dave Smith (Sep 7, 2016)

Tony---look at it this way---you are going to have to replace one end or the other no matter where you find the bad spot------a single female end is far better than the three way when it was new so that is a good improvement in your quest---I've cut the molded bad ends apart to see why they failed and found just-too much crammed into a molded end--some also include a light in there also-----I've never seen one that didn't show burnt marks around at least one of the three----at least by whacking it off with a couple inches of the cord will enable you to do a good test of  the rest of the cord---where I worked as a maintenance mechanic I could not convince the forklift drivers to move the cords instead of running over them----these were just single end cords  but would be shorted somewhere in the middle----then after finding the broken wires and  fixing them they complained about shorter length cords and I would have to make them up a new longer one---the worst ones for me were the overhead crane pendant  hand control  drops that got stretched  when getting caught on something or more often when the forklift  driver caught it  by not paying attention-------Dave


----------



## David S (Sep 7, 2016)

Take it to your dentist and have her xray it.

David


----------



## P T Schram (Sep 7, 2016)

Power Probe makes a device to find opens.

I use a telephone circuit tone generator and signal sniffer.

I wonder if the audio frequency isn't high enough to overcome some of the problems with the 60 hertz devices you're using, but I've found similar breaks using this method.

OR, you could research old issues of QST, the journal of the American Radio Relay League as this sounds an awful lot like the theory logic problems that used to be in the magazine when I was a little boy, long before I understood how/what was being done!


----------



## Tony Wells (Sep 7, 2016)

Dave, that's spoiling the fun of this exercise though. You're probably right, and I have industrial grade ends to put on when I do cut it. Just not ready yet. Remember, I have been laid up with a broken leg/hip since April, and still can't do much work, so this is giving my mind at least something to do. Then I go rig up and try it.  It will get to a point sometime when I will just cut the thing. Or chop it into little pieces and make a sandwich out of it. For now, it's just for fun. Like I said, I have cords, so it's not like I even need it.

P T, I have tried my Fluke fox  & hound, and surprisingly, still not been able to locate the break. It doesn't operate at 60 cycles. Not sure what frequency it runs, but it's not audio. I may try a signal generator instead of the tone unit, and dial around to see if there is an ideal frequency. I know my frequency counter can be varied in it's sensitivity by making a sort of antenna. I also have a couple of signal tracing units. I believe they require direct contact though. When aligning a radio, as you may know since you mentioned QST (I have a stack of old copies) you can direct couple to the radio, or inductively couple. I may be able to get the right combination of pickup method and vary the amplitude of the generator to get there. The twists in CAT are designed to eliminate cross-talk, but the twists in an extension cord don't take this into consideration, nor to they attenuate any of it that I can tell.


----------



## yendor (Sep 29, 2016)

One thing to know about the twists in the 4 pairs of CAT5 Cabling is each one has a different # of Turns per Inch.
This changes the actual Length of each pair and the Resistance of each pair.


----------

