Why won't this light turn on?

[John]

I have a ceiling light in the hallway with two light switches (dipoles?). The ceiling light has 4 bulbs. The other day the hallway light wouldn't turn on with known good bulbs.

Not knowing anything about electricity I *assumed* that one of the switches had to be defective so I replaced both on/off switches -- that didn't solve the problem.

There's electricity in both boxes to other lamps so I know (think) that it's not a circuit breaker problem.

Before proceeding any further (e.g. replace the lamp fixture), I bought a simple current tester to see if there's any electricity in either of the light switches.

Not knowing what/how to test, I put the test probes on each of the wires for both switches in every conceivable configuration. The diode never glowed.

Beside laying out a few hundred dollars for an electrician to deign making his royal appearance, what can I do first to resolve this problem?

[Speedy Jim]

Before you dig into it, study up here:

Jim

[scott21230]

"Not knowing anything about electricity I *assumed* that one of the switches had to be defective so I replaced both on/off switches -- that didn't solve the problem. "

Are you an auto mechanic by trade? From your above decribed behavior, I'd say so.

Have you checked to see if any of your breakers have tripped? Include any GFCI's in the house as well. You never know how many stupid things someone before you may have done so, putting an inside light fixture on a circuit after a bathroom or garage GFCI is certainly possible.

[Tony Hwang]

Brave man, sounds like you replaced switches without even bothering turning off the breaker at the panel? You should've checked breaker for the light fixture before anything else.

[John]

Auto mechanic? Bummer. No, a software engineer.

I first checked all the breakers and GFCIs. They're fine. When I turn a breaker on/off, it affects all the other lights in the box. Curiously, the switches are on two different breakers. Before starting to replace the second light switch, I was fortunate to accidentally flip another switch in the box and to my shock, the light turned on. I found the other breaker and turned it off.

How do I use the tester to verify that there's power coming into the light switches? If it was a single switch, I wouldn't be asking such a lame question.

[John]

Brave I am not. I turned off one breaker at a time until the other lights in the same box turned off before swapping out the switch. I didn't trust the labels at the breakers.

[Rich256]

Did you look at the site referenced by Speedy Jim?

What you have is the three way switch configuration. Did you replace the switched with the proper type (Three way)?

The four lamps are in parallel.

[John]

I'm looking at it now. I don't quite understand it yet. It'll take a bit of time to sink in.

Yes, I bought identical replacements and when I replaced the wires, I swapped them in the identical configuration.

Oh, when I took the lamp down I thought it was in series. One wire led to the next like in an Xmas tree.

Let me ask the question just one last time: How do I use the tester to see if there's any power reaching the switch to begin with?

[mm]

When I was 12, the Lionel train transformer didn't work. I tried more than once to look at it/fix it. I didn't have any meters or special tools. The last time I noticed that I'd taken the cover off and fiddled with it without getting a shock. From that I deduced it was the cord or plug, and it was the plug. This is no way to do things. Even at 12, I should have been more careful.

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[mm]

That might be part of the problem too. That's what I do for a living, and since I have a test environment that I can restore, I can make any mistake without too much trouble. Remember that your house is the production system.

It's more than curious. No one would install one light controlled by two swtiches with each swtich on a different breaker.

Did this used to work? How did it work: could you turn the light both on AND OFF from two different swtiches, no matter how the other switch was set.? If that is the case, I don't see how two breakers could be involved.

How many lights are "in the box"? How many switches?

So 3 different swtiches control this light? And 2 of them are in one location? If they are in 3 locations, maybe you have a four way switch. If I misunderstand, you probably don't.

You definitely have to read that website until you understand all of it. If it is really confusing (I haven't checked) you might get a book from the library, which might say the same thing in a different way,

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[Sev]

Yes, do be careful. It sounds like there is break in the circuit at some point before power arrives at the switch. You say you tested every possible configuration of wires and diode didn't light. Tester itself is good, yes? Check on known good receptacle, hot(small slot) to neutral or ground. Then with power on(wear gloves), check at each screw terminal of switches to any ground- bare wire in box or box itself if metal. If diode doesn't light, switches aren't getting power. You will have to trace circuit to see how they are fed. If you are lucky, you may see an obvious loose wire in one of these adjacent boxes. But since you say some of these appear to be on a different circuit, the break may be in a switch/ recep/ junction box in a nearby location. Can you identify everything which is affected when when you turn circuit off? The problem could be in one of these boxes. Actually, I'm now wondering if you are right when you say things are on different circuit- you mustn't rely totally on labels at panel- only trust what you test. Hope this helps a little- do consider getting someone more knowledgeable to help- even a pro- might not be as much as you think

[Sev]

Is it storytime? My older bro was very mechanically inclined- still is- half of the little I know I learned from him. As a kid, he fooled with transformers, too. Told me of occasionally getting shocked. At age 5, I was jealous of this gap in my experience, decided to close it by carefully sticking something metal in outlet. Oh! so that's what he was talking about.

[John]

Two switches at either end of the hall turn the light on/off.

The power tester is working -- I plugged into a known live circuit and it glowed.

There's another 3 way switch in the same box which I used to see how the power tester worked. To my surprise, it glowed when I turned the power to the light off.

There are several other light switches in each box. All unrelated to the hallway light. None of the other lights have any problems.

The hallway light was working fine up until the other day. There's no one else in the house who might have touched something.

One switch confuses me: There are two (2) red wires on one side. This doesn't match with anything in:

Another switch in the box have two (2) feeds, both black.

[John]

Never mind. The problem wasn't with the switches after all -- it was the cheapo ceiling lamp.

[Rich256]

Good for you!!! And you learned a few things.

About the parallel lamps. What that means is that the black goes from lamp to lamp and the white goes from lamp to lamp. If they were series there would just one wire in and one out.

Parallel:

Power ------------------- L L L L Return-------------------

Series:

Power -----L------L------L-----L-----Return

[mm]

Literally LOL.

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[mm]

Glad you got it. "Remember, if it weren't for cheap things, we wouldn' t have so many things."

Right, and they don't do series with 110 volt lightbulbs. I thought he said 2 or 3 lights were in series but if they were 110 they couldn't have been.i

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[Mark Lloyd]

I've replaced light switches with the power on, but only in simple setups (no wires in the box except those TWO). I even touched the hot wire once, and didn't feel anything. Just don't touch anything else conductive at the same time.

[Mark Lloyd]

A relative once thought I got interested in electricity after putting a finger in a live light socket. Actually that felt like a few hundred ants crawling around UNDER the skin.

[electro1]

responding to

electro1 wrote: Thank you times a billion Scott. I just finished wiring two new lines all the way from one end of my house, up through the attic, and down into my garage when the hall lights went out on me without any breaker in my box flipping off. I replaced the bulbs to no avail. I then went to home depot quickly to get new switches before testing if there was power to the outlets because home depot was about to close. When I got home, I tested the wires in every possible way I could and I couldn't get my volt meter to light up, so I changed the switches. Things still didn't work. I really wish I would have read this post, because I spent about 20 minutes up in my attic trying to see if maybe I knocked some wires loose while installing the new wires. Finally I gave in, and searched and found this thread, mentioning the GFCI's. Yep, the bathroom had a GFCI that had tripped......Next time I'll know where to start the diagnosis......once again, thanks times a billion.

-Gabe

[e-mail] wrote:

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