I have an odd issue that I cannot figure out in my upstairs game room. Vaulted ceiling, 3 lights. 2 lights on one side (attic accessible)and the 3rd light on the other side that backs up to the roof deck (unaccessible).

I have a three way switch that controls the lights; typically we use the switch by the stairs where you enter.

About 2 years ago I switched the 2 lights from the old-school 80's can light to the puck LED lights. Before, I had LED bulbs in the fixture, but wanted to increase insulation and switched to the pucks. Now, about 2 months ago, only one light will come on.

Before, with the old can lights, the light closest to the 'main' switch we use would not light up, but then turn on. When it did not turn on (as it is not turning on now), the 3rd non-accessible light won't light up either. I bought 6 puck lights and still have 3 leftover. Last month, I switched the non-working puck light with a new kit, still not lighting up. I switched the puck light from the non-working one with the working one and the physical light will turn on. The wiring hasn't changed; I literally unscrewed the old wiring and plugged into the new box connectors (clear plastic that you push in and friction holds in).

I'm getting power to the non-functioning light, but it isn't coming on. Any ideas?

I have no idea how it is wired upstairs. I believe the working light is 1st, but not sure if it goes over the cathedral ceiling to the 3rd light (original can) and then back to the non-working puck light or if it goes puck to puck then old can. The non-working puck light has two wires going to it, not just one. Not sure if that's the switch leg or the 'continuing on' leg.

TIA for help.

~egon

Have you checked the polarity at each light? If you have one reversed, it might cause such a problem...

Unlike incandescent bulbs, LEDs won't work unless the polarity is correct.

I read your post about 7 times and I can't quite follow your description. Too much of a mix of what used to happen vs what is happening now, and difficult keep straight which light is which. Sorry.

That said, my gut says you have a loose neutral somewhere, possibly on the "inaccessible" light. Even those it seems inaccessible, you can typically pull the can out, and there's access to the box from the inside the fixture. It's not kosher to have a junction that's inaccessible, so the fixture manufacturers make them accessible (but not fun).

A couple of follow-up questions:

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I'm getting power to the non-functioning light, but it isn't coming on. Any ideas?

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Are you using a non-contact voltage tester, or a multi-meter? You may be getting power on the line side, but the neutral may be disconnected elsewhere, so it looks like you have power, but you don't actually have a complete circuit. Test the resistance between the ground wire and neutral at this location. If infinite, neutral is loose somewhere.

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Before, with the old can lights, the light closest to the 'main' switch we use would not light up, but then turn on.

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Do you mean that the light would not turn on when the switch was flipped, and then after some seconds/minutes/hours, it would turn on?

Is there any difference depending on which switch you use?

UnderoosAg said:

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dudeabides said:

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Have you checked the polarity at each light? If you have one reversed, it might cause such a problem...

Unlike incandescent bulbs, LEDs won't work unless the polarity is correct.

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AC power doesn't have polarity.

Ditto on the loose wire. Or you lost the traveler somewhere between the three ways. If you get a wire out of place with three ways, you can get a hair pull out situation where flipping a switch will give you 120 hot to neutral or ground at one light but not at the others, and then the opposite when you flip the other switch. Might have to ring out the wires at each can and the switches with an ohm meter.

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Where did I say AC?

You think all LEDs run straight off AC?

Most LEDs run off DC. There is usually a transformer in between the home AC and the LED. Sometimes the transformer is built in, sometimes it is a separate junction box. Given what the OP stated, I assumed that ONE possibility is that he has a separate transformer and the polarity between it and the LED was reversed.

Sorry for the delay, but posting photos.


Lights I installed/bought



Internal connectors.


Back of the box.



Wiring (crude) diagram.



Room with the lights 'on'.

I did not or have not brought my multimeter up to test voltages going to the boxes, but I pulled all the wires apart and tested for voltage with the non-contact sensor I have (hot or not). But if I didn't have a complete circuit, then why would one light come on?

As before (with the old can lights), there were times when you flipped the switch and none of the lights came on. But after some time (less than an hour, more than a few seconds), all the lights would come on. The same occurrence happened after I switched 2 of the can lights.

I have tried changing the switch positions (the one by the stairs is normally 'off' when the lights are off and the other switch is 'on'), but does not seem to be the issue. I thought maybe the switch was going bad, but haven't been able to figure out how to fully test.

~egon

Dr. Docto said:

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But if I didn't have a complete circuit, then why would one light come on?

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May be easiest to explain with a picture. These lights are wired in parallel.

Here's a possible configuration of your system.



There are a couple of places you could have a bad or loose connection (Examples noted).
- If Example #2 was completely loose, you would still have a completed circuit at light #1.
- If only Example #1 was completely loose, you would have a completed circuit at lights #1 & #2.
- Or, you could have a shoddy connection at Example #2 in the wirenut, and sometimes, when the weather is warmer and the copper is just slightly expanded due to heat, you have a good connection that allows power to flow to all lights after a certain amount of warmup time. Sometimes you see wirenuts like this with three or more wires and the third wire isn't really tight in the connection.

It's hard to say exactly, since your circuit may be slightly different, but functionally, this is how it works.

If the "hots" are all intact, you'd still see voltage at all locations with a non-contact tester, but there's not a return current path on the neutral to complete the circuit.

Dang, that neutral was doing its best to transition to a hot!

Glad you found it.