How to test and replace vanity light fixture?

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Old 01-07-17, 04:10 PM
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How to test and replace vanity light fixture?

Okay guys, so in our bathroom, we have a double switch plate. One is for the fan, and one is for the vanity light fixture. The light fixture isn't working. I turned off the electricity to the switches. I opened the switch plate and saw two individual light switches inside. I replaced the switch to the vanity light, and that did not work. Vanity light fixture still not working.

Before I call an electrician, I'd like to eliminate the light fixture because I think it's something I can replace on my own. I happened to receive a multimeter for Christmas of 2015, but never opened it.

Firstly, I take It I can use it to test the fixture? But I have no knowledge of these things or electrical lingo. Can someone look at the picture of the Multimeter and give me step by step instructions on how to test the fixture? But I guess we would have to test the wires from the wall too, right? Because we don't know if it's the wires from the wall or the fixture that's the issue, correct?

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Secondly, I've detached the fixture from the wall. Not completely detached. The wires are still bound together. If I needed to replace the fixture, how do I disconnect these wires? Untwisting doesn't seem to work, and it doesn't look like the wires are twisted inside the cap. There is actually some sort of gold plate inside, and I think maybe the wires are inserted into it or something. I've attached a picture so if anywhere recognizes this type of cap, maybe you can advise on how to disconnect. Do I just snip it at the base and re-strip for the new fixture?

Thank you in advance!

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Old 01-07-17, 04:35 PM
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OK..... I'll be right back with meter instructions. In the mean time.... those are crimp caps because you have multiple sockets being combined. The splice with the wirenuts is behind the wall mounted plate. They should be in a junction box.

Your junction box is where the red circle is and the wires are crushed behind the fixture.
The junction box is supposed to be where the blue circle is.

Someone goofed on the mounting box location..... probably off center.

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Old 01-07-17, 05:18 PM
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For the most part you will be using three settings on that meter.
When you're working on home/live AC.... you'll use the ACV position.
When working on low voltage DC like in a car..... you'll use the DCV position.
For checking for shorts and continuity.... you'll use the OHMS scale.
The OHMS scale can only be used on dead circuits.

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Old 01-07-17, 05:30 PM
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Thank you PJ, but I'm sorry I still need more guidance. You'll need to treat me like a child and assume I don't even know the common sense or common knowledge stuff. LOL! So here are some questions..

1. When testing, does electricity to switch need to be on or off?
2. So I'm testing for OHMS here?
3. The red and black probes, do I use both? Where am I pointing? To black or white wires of the fixture itself, or the wires coming from the wall?
4. What reading or sound am I looking for that would indicate fixture is still good or dead, or there is no electricity going through the wall wires?

LOL! Sorry PJ! Thank you for your time.
 
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Old 01-07-17, 05:39 PM
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Turn the meter on to AC. Since we are measuring AC there is no polarity with the probes.

With the switch on to the light..... put one probe in the white cap crimp and the other probe in the black cap crimp. You should measure 120vac. Let us know.
 
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Old 01-07-17, 06:07 PM
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Before I do that, do I leave electricity on or off at the breaker?
 
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Old 01-07-17, 07:13 PM
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do I leave electricity on or off at the breaker?
You can't measure voltage if the breaker is off. Breaker off there should be no voltage.
 
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Old 01-07-17, 08:24 PM
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Got it. Just wanted to be sure because anytime I read or watch about these things, they always grill in your head to turn off the power.
 
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Old 01-07-17, 08:28 PM
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Okay, so it does say 120. Does that mean the wires are okay, and the fixture is the problem?
 
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Old 01-07-17, 09:06 PM
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Check for voltage between the tab and the shell of the bulb socket.
 
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Old 01-07-17, 09:38 PM
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Are you sure the bulbs are ok.

If you're not sure.... they can be checked with your meter.
 
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Old 01-07-17, 09:52 PM
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Bulbs are definitely okay. We simply tested those onto another lamp.

As for "voltage between the tab and the shell of the bulb socket," I'm not sure how to properly do that. There are three sockets, so I know a socket. But not quite sure the meaning of "tab." And do I just stick both probes into the socket and touch any part of the metal? Am I still looking for 120v? Or, what reading would indicate bad socket?

Here are pictures of my fixture and a close up.

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Old 01-07-17, 10:05 PM
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The tab at the bottom is one conductor the metal shell on the side is your other conductor. Yes, ~120 volts.
 
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Old 01-07-17, 10:16 PM
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One more thing, just to make sure. Lets go back to the beginning when I replaced the switch. Attached are the pictures of the OLD and NEW switch.
I want to make sure that it does not matter that I didn't buy the exact kind? Because the old one had the two wires going into it directly from the back and there is no ground screw. The new one is the kind where you wrap the wires around the screw, and there is a ground screw. But there was never a ground wire, so I figure I can just leave it empty. It didn't matter that I didn't get the exact switch did it?

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Old 01-07-17, 10:43 PM
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Okay, when I touch tab at the bottom and side indicated by the red circle, I get 120. Here is a picture to make sure I'm understanding what you're saying.

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Old 01-07-17, 11:08 PM
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Okay guys, we have a bit of a breakthrough.......

When the fixture is loosen from the wall, the switch will turn on the lights. That's why when I was testing it as you guys instructed, everything was giving 120, including tab/shell test. I just noticed the lights coming back, so I didn't question it. I just started to clean up. Pushed the fixture back, placed back the decorative glass shells, etc. It was a complete waste of time because the lights didn't work again. So I did the socket/tab/shell testing while the fixture was completely against the wall, and I was only getting about 40 volts.

I loosen the fixture again, just to make sure my mind is not playing tricks on me and sure enough, the lights came back on. I even had my wife come watch as I press back the fixture to show her how the lights will stop working, and sure enough, it stopped when I pressed the fixture back to the wall.

So the conclusion here is that when the fixture is loose and detached from wall, it works. When it's pressed against wall, it doesn't like it. So are we talking about some sort of loose wiring that are going into the sockets? Why would it hate to be pressed against the wall though? Doesn't that just push all the wires tighter, isn't that good?

Do you guys have a better understanding of what might be going on with this new found discovery? That it doesn't like being pressed against the wall?
 
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Old 01-07-17, 11:33 PM
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Yes..... look at the wires scrunched under the back plate in picture 2. They go to a splice point behind the fixture mounting plate. You will have to remove the fixture back plate to access the splice behind it.
 
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Old 01-08-17, 12:16 AM
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Pj, you see that black rectangle.. Why couldn't I simply cut that out? Give room for the wires to go through? Any reason I shouldn't do that? I have a drill press. Thinking of using a small bit and just work my way... Or, a hole saw bit?

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Old 01-08-17, 12:47 PM
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Mission accomplished! Thank you all for your advice. The splice in the back was indeed loose. When I undid the twist cap, I can see that there was not enough exposed white wire, so I simply cut it off and re-stripped a fresh length and wrapped it neatly around the solid wire. Did it for both black and white, and now when I push the fixture back against the wall, the light still works. So all is good!

For my educational purpose, can someone explain the meaning of wires that are made of strand versus the solid one piece wires? Is it simply for flexibility because it would be tough to twist two solids?
 
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Old 01-08-17, 12:53 PM
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Stranded wire pulls thru conduit easier and is more flexible. It is harder to use on devices like switches and receptacles as the strands won't stay under the screw terminals.

You'll usually find stranded on light fixtures as it's more flexible to work with.
 
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