Troubleshooting recessed can light

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Old 07-28-14, 04:30 PM
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Troubleshooting recessed can light

Hi all, this is my first post here. Pretty limited electrical knowledge, but wanting to learn how to troubleshoot household issues better. So here goes...

I have a recessed can light in the basement that is not working, and I can't figure out why. We have lived in the house for 4 years now and it has always worked until about 6 months ago. I turned it on and the light blew out, and it has not worked since.

I spent some time troubleshooting and here is what I know. The light is on a 3 way switch. There is a normal light switch at the top of the steps, and dimmer switch at the bottom of the steps. This is the only light wired in the circuit. I measured 120 volts at the socket with my meter but no light bulbs are working (I checked known good light bulbs).

At first I thought it might be the tab that connects to the base of the light bulb, so I flipped the breaker off and tried bending it out with a small screw driver. No luck. In fact, I can tell that the bulb is making contact because the dimmer switch has an indicator light on it that lights up when the bulb is in (it is supposed to light up when the power to the light is off, but only does so when a bulb is in place).

So I'm a bit stumped as to what to test next. I took the can out of the ceiling and pulled both switch plates off, the wiring seemed OK to me (no obviously loose or damaged connections) but I get a bit lost with the volt meter in there... not great with electrical so not sure how to test.

Unfortunately the fixture is the kind that mounts to the joists (new construction) and taking it out will probably cause damage to the drywall - otherwise I would have already tried replacing the fixture. But I'm not convinced that the fixture is the problem since I'm getting voltage. I believe it is this model: Halo H7T, 6" Housing Non-IC 120V Line Voltage - Recessed Light Fixture Housings - Amazon.com

EDIT: originally I said that I thought this one didn't have a thermal switch, but apparently it is "thermally protected"... but I can't find where the thing is!

Any ideas?
 
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Old 07-28-14, 04:34 PM
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Welcome to the forums.

Did you measure 120vac from the center pin to the shell using a voltmeter ?
 
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Old 07-28-14, 05:48 PM
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Hi PJmax - yes, I measured 120vac from the center pin (or tab) to the shell. It might have been something like 118v; is it normal for it to vary by a couple of volts? Will double check that again tomorrow if needed. I think it was measuring that way regardless of the switch being on or off. But still no light!
 
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Old 07-28-14, 05:58 PM
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Actually just got the voltmeter out and checked again to be sure since it's been a while. On the broken fixture in question, I measured ~116-118vac regardless of the state of either switch. I am getting voltage whether the switch is on or off. I don't know if that's normal for a 3 way switch?

On one of the working fixtures (we have 8 installed on a dimmer switch for the rest of the room) I got ~106vac when the dimmer was all the way up, and 0 when off... which makes a lot more sense to me.
 
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Old 07-28-14, 06:24 PM
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You should have close to 0 volts with the three way switch off. It would be helpful to check that voltage again with a working bulb in the socket. You should be able to drop the socket down to working height to get a voltmeter in there.
 
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Old 07-29-14, 04:43 AM
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K, I dropped the socket down and measured from the back of the socket with a working bulb in it. Getting 0.15v when the switch is on and all the way up. With the switch off, It was close to 0, ~.02v or something.
 
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Old 07-30-14, 12:35 AM
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Ok...... so you aren't getting any power to the fixture.

Check from black or center pin to ground. If you measure 120v then you've lost a neutral connection.
 
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