Author Topic: Troubleshooting electricity problem  (Read 9032 times)

Manguy888

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Troubleshooting electricity problem
« on: May 27, 2015, 10:18:24 AM »
I have a ceiling light that was working only sporadically, then not at all. Here are the steps I've taken to troubleshoot.

1. Switched in another light - still doesn't work. conclusion: not the light itself
2. Checked the power at the light switch - 120 volts. Conclusion: electricity good at the switch
3. Here's where things get weird:
     a. Used multimeter on ceiling wires, see 120ish volts
     b. loosely attach light and have wife flip switch. Light goes on for a second then flickers off
     c. use multimeter again, only register 70-80 volts
4. Noticed that wires at the switch are newish looking, while the wires on the ceiling are old and cloth covered (I have an old house, this isn't unusual). Since the switch goes right to the light, shouldn't they be the same.

My hunch is that either the older wires have a break somewhere causing an inconsistent connection, or there's a junction box somewhere where the new and old looking wires join up.

Any savvy mustachians have any other idea for me? I'm trying to avoid hiring an electrician, and I feel fairly confident in my T/S skills.

mikesinWV

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Re: Troubleshooting electricity problem
« Reply #1 on: May 27, 2015, 10:28:50 AM »
Assuming the old cloth wires are black.  Sounds like knob and tube.  I have it in my 100+ year old house. 

Is there any way you can find the box where the "new" and the "old" wires are connected?

Manguy888

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Re: Troubleshooting electricity problem
« Reply #2 on: May 27, 2015, 10:46:34 AM »
the knob and tube was replaced at some point, but some of the older wires remain.

Job for tonight will be to try to trace the wires. There's no obvious spot for a junction box, but I know it would be a major no-no to have one hidden in a wall or ceiling

mikesinWV

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Re: Troubleshooting electricity problem
« Reply #3 on: May 27, 2015, 10:57:08 AM »
In the 3 old houses that I've lived in, the knob and tube may be mostly removed but often they leave it in ceilings and or walls b/c it is such a pain in the as* to remove.   And, generally it hasn't been disturbed so generally not a big deal.

Are the cloth wires in a single wrapping (individual wires wrapped separately) or are they completely separate?  That is, do they look like modern romex?

While junction boxes that are not accessible is against code now it doesn't mean it wasn't done previously. 


Manguy888

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Re: Troubleshooting electricity problem
« Reply #4 on: May 27, 2015, 11:00:27 AM »
The wires are separate - each has its own wrapping. You can generally tell them apart because one will have lighter colored cloth than the other. They definitely don't come in together like with the modern 14/3 stuff that I buy

Thanks for your help

phred

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Re: Troubleshooting electricity problem
« Reply #5 on: May 27, 2015, 12:11:42 PM »
One floor house?  Take a looksee up in the attic for a junction box.  First thing I would do is substitute the switch; sometimes the spring wears out

Jack

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Re: Troubleshooting electricity problem
« Reply #6 on: May 27, 2015, 12:49:44 PM »
the knob and tube was replaced at some point, but some of the older wires remain.

The wires are separate - each has its own wrapping. You can generally tell them apart because one will have lighter colored cloth than the other. They definitely don't come in together like with the modern 14/3 stuff that I buy

Well then, apparently, only most of the knob and tube was replaced.

3. Here's where things get weird:
     a. Used multimeter on ceiling wires, see 120ish volts
     b. loosely attach light and have wife flip switch. Light goes on for a second then flickers off
     c. use multimeter again, only register 70-80 volts

My E&M physics is pretty rusty, but measuring 70-80 volts when you're expecting 120 strikes me as a "something's heating up and about to catch on fire" kind of problem. Personally, I'd keep the circuit turned off at the breaker (or maybe fuse, in your case) except when actively troubleshooting it, and be very careful about it even then.

phred

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Re: Troubleshooting electricity problem
« Reply #7 on: May 29, 2015, 07:40:24 AM »
one of the receptacle boxes may be used as the "junction box".  Check all those in that room and in neighboring rooms.  Hopefully, you don't find any aluminum housewire

jba302

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Re: Troubleshooting electricity problem
« Reply #8 on: May 29, 2015, 08:03:21 AM »


My E&M physics is pretty rusty, but measuring 70-80 volts when you're expecting 120 strikes me as a "something's heating up and about to catch on fire" kind of problem. Personally, I'd keep the circuit turned off at the breaker (or maybe fuse, in your case) except when actively troubleshooting it, and be very careful about it even then.

This is the first thing that came to my mind as well. Might be something loose in the switch but if you can access the wires I'd replace them asap.

Manguy888

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Re: Troubleshooting electricity problem
« Reply #9 on: May 29, 2015, 08:17:55 AM »
Thanks for all the advice guys. Since it's 120 at the switch and 70-80 at the light, it's my feeling that the problem is in that wire path and that as long as the light switch it off there's no danger of fire. I've got tape over the switch and everyone knows not to touch it.

My plan is to take some time over the weekend when I can have the breaker off and trace the path to find the junction box and replace the whole wire path with new 14/3 romex. If I have issues doing this I'll call an electrician.

I've done a lot of electrical work in my house and I've never found any aluminum wire.

Spork

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Re: Troubleshooting electricity problem
« Reply #10 on: May 29, 2015, 10:04:55 AM »
Do you have (or can you borrow/purchase) a toner? 

They look like this:  http://www.amazon.com/Triplett-3399-Fox-Hound-Probe/dp/B001ULPREW

If you have any IT friends, they might have one you can borrow.

If you turn off the circuit and attach the toner to the wire at the light... you can probably follow the wire behind the wall with the wand.  It might help you trace that back.

bzzzt

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Re: Troubleshooting electricity problem
« Reply #11 on: May 29, 2015, 05:57:43 PM »
Could be a bad splice, partially broken wire, burned up neutral, hack job remodel, ground used as neutral, list goes on.

I'd check the connections that you can get to (terminations, splices, etc)

Your best bet is to replace the wiring if you feel competent.

paddedhat

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Re: Troubleshooting electricity problem
« Reply #12 on: May 29, 2015, 08:16:14 PM »
Could be a bad splice, partially broken wire, burned up neutral, hack job remodel, ground used as neutral, list goes on.

I'd check the connections that you can get to (terminations, splices, etc)

Your best bet is to replace the wiring if you feel competent.

The one known as BZZZT is very wise. If I had to guess, I would say that wisdom was hard earned.

Take a moment and pray to the gods of stray electrons that you are not running into either a open neutral (particularly if there is a three wire circuit involved), or a grounded neutral. Having done far too much residential troubleshooting, or as it's more commonly called, "stalking the trail of idiots", both of these problems can be one crazy PITA to track down. You sound plenty competent. Take the time to run fresh Romex from the switch box to the light. Don't forget to dispose of the existing switch, they can also intermittently fail, and drive you half nuts, until you figure it out. I have even seen switches, fresh out of the box, that will fail intermittently. Good luck.

Heckler

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Re: Troubleshooting electricity problem
« Reply #13 on: May 30, 2015, 10:05:27 AM »
You replaced the light or the light bulb with no effect?   

It could be the contact inside the socket under the centre point of the bulb that's lost it's spring.  Simply turn off the breaker, remove the bulb and carefully bend the contact back up at a 30 degree (approx) angle, so that it contacts the bulb better.

(The brass piece in the middle of this picture)



Just make sure the breaker is OFF, or you'll be joining Mr. BZZZT!
« Last Edit: May 30, 2015, 10:08:02 AM by Heckler »

bzzzt

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Re: Troubleshooting electricity problem
« Reply #14 on: May 30, 2015, 09:10:03 PM »
I was just thinking of another scenario. You didn't add any GFCI receptacles lately, did you? I ran into that once where someone replaced the device but swapped the Line and Load neutrals when they hooked it back up.   It was upstream of the stuff that now "quit working" and they didn't tell me about it until I found it: "Oh, I didn't think it was related since they're different rooms"... *facepalm*

Manguy888

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Re: Troubleshooting electricity problem
« Reply #15 on: June 01, 2015, 01:24:23 PM »
Thanks for the advice bzzzt. I was away this weekend but I'm going to take some time tonight to troubleshoot - I'll put the results up here.

paddedhat

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Re: Troubleshooting electricity problem
« Reply #16 on: June 01, 2015, 02:24:48 PM »
I was just thinking of another scenario. You didn't add any GFCI receptacles lately, did you? I ran into that once where someone replaced the device but swapped the Line and Load neutrals when they hooked it back up.   It was upstream of the stuff that now "quit working" and they didn't tell me about it until I found it: "Oh, I didn't think it was related since they're different rooms"... *facepalm*

Most homeowners are totally unaware of the "long and winding road" that branch circuits travel, especially if they have been added to over the years. I have spent hours chasing down a loose neutral at a receptacle since it was on a GFCI circuit and the "Electrician" started in the garage, did all the outside outlets, then worked his way through all the bathrooms in the house, with the same circuit. I'm pretty sure the electrons were tired by the time the got to the last outlet:)  I have also done several service calls where the bathroom receptacle suddenly is dead, and it was daisy chained through a GFCI outlet that is outside and hidden by a bush, or under a workbench in the garage. In these cases, the homeowner was not only surprised to find out that the hidden outlet was the problem, but they had no idea that the thing even existed in the first place. 

Manguy888

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Re: Troubleshooting electricity problem
« Reply #17 on: June 02, 2015, 05:40:29 AM »
Well, I peeled back one more layer of the onion last night.

I pulled out the switch and tugged on the new wires. Fortunately I just removed a drop-ceiling so I have more access than I normally would. I found a spot where the new wires were spliced into old. So even though this seemed not-kosher, the wires were still connected well IMO. However, playing around with this did not fix the '80 volts at the ceiling' problem.

I'm posting pictures of the ceiling, the splice point, and the switch box. Since my plan is to run new wire, I think I am going to pull out the ceiling box tonight. This won't be easy since it's a big heavy cast-iron thing and it appears that they plastered right over it (old houses - am I right??). The good news is that this branch only appears to have this light and one other hallway light, so I can leave it off indefinitely while I troubleshoot.

If anyone has any input, I'd really appreciate it. You've all been really helpful so far.

paddedhat

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Re: Troubleshooting electricity problem
« Reply #18 on: June 02, 2015, 08:29:30 AM »
Well,  the boxless splice is a big code and safety issue. It appears however, that what you have is unswitched power to the ceiling box, then a switch leg dropping down to the switch box. This would mean that you can test for clean 120V at the ceiling box. The hot (black) leaves ceiling box on the white to the switch and returns on the black.  Take the remaining wirenuts off. Isolate the wires heading to the switch. Test the unswitched supply wires and see if they have a constant 120V. supply.  Hook a light up to this set of wires and leave it on, see if it functions well. This testing will isolate the issue, and determine if it's in the supply, or the switch leg.

Manguy888

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Re: Troubleshooting electricity problem
« Reply #19 on: June 02, 2015, 09:08:11 AM »
Paddedhat - thanks for the response!

I am completely with you until the line "hot (black) leaves ceiling box on the white to the switch and returns on the black". Then I start to get confused as to what exactly I should be troubleshooting.

I'm reattaching the pictures with some big honking letters on each node. If it's easy to just say 'remove wire nut from D, test A and B' or something like that, it would make it super clear.

guitar_stitch

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Re: Troubleshooting electricity problem
« Reply #20 on: June 02, 2015, 12:08:22 PM »
Power is coming from the circuit breaker on the black wire in junction "B".  The white wire in "B" is going down to the switch.  Power returns from the switch through "C".  "A" is the neutral going back to the panel.

From the breaker box, power flows like this:

B (black) -> B (white)
B(white) -> D
D -> F

<switch here>

G -> E
E-> C

The light fixture goes between "A" and "C" with "C" being the 'hot' side.

Manguy888

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Re: Troubleshooting electricity problem
« Reply #21 on: June 02, 2015, 12:24:10 PM »
guitar_stitch - perfectly clear - thanks so much!

I'll pull apart from of the wire nuts and troubleshoot tonight

paddedhat

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Re: Troubleshooting electricity problem
« Reply #22 on: June 02, 2015, 06:52:14 PM »

http://ww2.justanswer.com/uploads/UR/urelectrician/2012-12-02_235756_power-into-light-wiring.gif

This link is a diagram of your situation with three exceptions. First, the yellow represents a ground wire which you do not appear to have. Second, the white wires are correctly remarked with black tape since they are no longer used as neutrals. Third,  your cluster-F has an illegal splice between the ceiling box and the switch box.

My assumption is that you will find that wire A and the black wire in splice B are part of the same cable. Confirm this by feeling and looking inside the box. If this is correct, this is the unswitched power being supplied by the panel. Remember, this can be doing a lot of other things between the panel and your ceiling box, and that MAY be the problem. With both wires safely exposed, turn the circuit back on and test for 120 Volts, at the bare ends of these wires. Also take a reading from the hot wire to the metal box to see if you have a grounded box, which is unlikely. If I'm guessing well so far, that means that the white wire from splice B and  black wire C are another cable, and this is your switch leg. Now this entire switch leg needs to be replaced anyway, since the illegal spice has to go, so tear it out and run a new Romex. The diagram should make everything clear. Good luck.

Manguy888

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Re: Troubleshooting electricity problem
« Reply #23 on: June 03, 2015, 06:15:46 AM »
So last night I unscrewed B and tested B-black to A. This read 80 volts. I understand this to mean that not enough power is coming in to power the light. This means that the switch leg is not the 'problem', although it has to be replaced anyway because of the illegal splice.

My next step is to figure out where the power is supplied from (it's not immediately obvious). There's only one other light on this branch, so it's not very complicated; however, it doesn't look like it's easy to trace the cable from the breaker box without taking the cover off and exposing the wires. Not sure if I'm ready for that yet.

This has been really helpful, even if I end up having to call a professional I've learned a ton.

paddedhat

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Re: Troubleshooting electricity problem
« Reply #24 on: June 03, 2015, 07:20:49 AM »
Interesting. Next step is to turn off all the 120V breakers in the panel except the circuit in question, and confirm that you are only seeing power at these two lights. My guess is that you might fine something, a room full of receptacles, or something else you did not suspect, that is also part of the circuit. Once you  determine exactly how many devices (lights and receptacles) and junction boxes are on the circuit, it's time to do what you have been doing so far. That being, taking the switches and receptacles out of the boxes, and taking a look at everything. At this point you should probably go to HD, or Lowes and grab a "non-contact voltage tester" this is an inexpensive pen like device that can tell you if you are working on a hot wire by touching the side of the insulation. When it comes to trouble shooting, I constantly use one. It gives you the chance to determine that everything in a junction box is dead, before you start digging around. One trick on this journey. If you find that you have a dozen devices on the circuit, go to the half way point, disassemble the circuit there and check voltage. If you find 120V, go to the half way point between where you are, and the end of the circuit. Never start at the end of a defective circuit and work backwards, it can be a huge waste of time.

mikesinWV

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Re: Troubleshooting electricity problem
« Reply #25 on: June 03, 2015, 07:52:36 AM »
Taking the cover off the breaker box is not a big deal.  When the cover is off don't go sticking a screwdriver or a finger in there touching wires or bars, etc.  Just use good sense! 

I too recommend the non contact voltage tester.  I use it all the time when I go exploring the wires in my house.  It simply lights up/beeps when there is voltage in a wire.  It does not tell you that it's a 110V, etc. 

guitar_stitch

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Re: Troubleshooting electricity problem
« Reply #26 on: June 03, 2015, 02:54:03 PM »
This is definitely a strange case.

Given that you've already uncovered some janky wiring, I would be inclined to pull all outlets, switches, and fixtures to inspect for poor practices.  You may uncover a weak neutral there.

If you get to the breaker panel, depending on the type you have, you will find that you have one to three bars with set screws to the sides of the breakers (and possibly to the bottom).  These bars will should have all white and bare copper wires in the positions.  You can safely check to ensure that each of these is cinched down very tight.  I have found more than one loose neutral in breaker panels that was causing problems.

Manguy888

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Re: Troubleshooting electricity problem
« Reply #27 on: June 04, 2015, 05:57:25 AM »
So I pulled the cover off the breaker box last night. As advertised it was not a big deal. All the wires are cinched down tight. I was able to trace my branch to where it leaves the basement. I think I've identified a junction box in a closet where the wires go to, but I can't be certain.

I've got a non-touch volt tester coming in the mail tomorrow and I'll use that the check the box for power. If there's no voltage, it's my box.

Let's say I do find where the issue is. Considering many of the runs are in ribbed metal conduit, do you think it's possible for me to just pull the old wires out and snake new wires into the existing conduit? Or do I have to replace the whole thing? My dream scenario is that you twist the new wires to the old wires at one point and pull at the old wires from the other end - maybe I'm being too optimistic

mikesinWV

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Re: Troubleshooting electricity problem
« Reply #28 on: June 04, 2015, 09:03:15 AM »
if this "ribbed metal conduit" is what I think it is, you will have a difficult time trying to pull wires out of it.  also note that your voltage tester may not register power if you touch the metal conduit.  if you can touch the actual wire or the cloth around the wire with the tool, that'll give you a better read.


Manguy888

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Re: Troubleshooting electricity problem
« Reply #29 on: June 04, 2015, 10:01:56 AM »
I opened the box and will be able to touch the wires directly

paddedhat

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Re: Troubleshooting electricity problem
« Reply #30 on: June 04, 2015, 12:40:05 PM »
It's not flexible metal conduit, it's a metal clad cable, which is a factory built assembly of the wires and the metal wrapping. Generally, in residential work, it has been completely replaced by Romex, which is the plastic clad, multi-wire cable. The very early stuff you have is designated BX, which was a cable that relied on the metal jacket being the ground. Newer products are MC, which has a full sized ground wire.

Typically you would want to avoid using new metal clad cable as it is expensive and requires special tools and skills.

Manguy888

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Re: Troubleshooting electricity problem
« Reply #31 on: June 12, 2015, 08:09:44 AM »
Hey all - one final update for those who gave me so much help.

I called a local electrician and worked along side him this morning. The problem was a bad neutral wire somewhere in path back from the light. TS'ing this would have meant notches all along the plaster walls and ceiling, so we made the decision to run new wire to the light from a junction box just beneath it in the basement.

The bad run of wire, illegal splices and all, will remain in the wall but it is de-energized and capped off. By working with the guy, I probably shaved an hour off the time to complete (and the resulting $), and I learned enough that I'm confident I'll be able to fix the next problem like this that comes around.

Final damage should be around $150.

Thanks everyone for your help!

mikesinWV

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Re: Troubleshooting electricity problem
« Reply #32 on: June 12, 2015, 09:47:11 AM »
Great news.  150 bucks isn't bad.  And you got to learn something from all this. 

guitar_stitch

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Re: Troubleshooting electricity problem
« Reply #33 on: June 12, 2015, 02:21:24 PM »
$150 for a licensed electrician to TS and fish wire?  That's a steal!

paddedhat

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Re: Troubleshooting electricity problem
« Reply #34 on: June 12, 2015, 07:01:49 PM »
$150 for a licensed electrician to TS and fish wire?  That's a steal!

Yea, that the kind of number you would see in my area.......................thirty years ago.