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I spent the good part of my Saturday installing some fancy light fixtures. The crescendo was supposed to be when the lights came on but instead, I got a small pop and a flash of light behind the switch. I know I did the wiring correctly on the fixture.
I noticed the panel behind the switches has 6 power cables coming out to three light switches. I'm wondering if the wiring is incorrect on this. We purchased the home without an installed fixture in this spot so I can't tell if it's ever worked there.

Here's a photo to show the wiring. Any help would be greatly appreciated.
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Another photo enter image description here

And here's a diagram of the wiring: enter image description here

Here are additional photos:
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    Did you touch the switch wiring or just the fixture wiring? Those whites on the switches are not neutrals, but what are called travelers. Did you check/make sure only a single breaker controls the power to all three switches?
    – crip659
    Commented Jul 14 at 22:29
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    Multiple quality issues here. Which switch supposedly controls the fixture location? Did you change any switch wiring, on any switches? Which ones? Did you take "before" pictures? Post them. Pictures of the wiring at the fixture location. If there never was a fixture installed at the location, your confidence in having wired it correctly may be misplaced. Usually the "switch blows the breaker" means you shorted a switch loop because you don't know what a switch loop is, and you should definitely learn that before working on installed light switch wiring.
    – Ecnerwal
    Commented Jul 14 at 22:38
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    We can't see what you don't show us. And all too often there's something there to see in pictures that someone lacking experience fails to notice, and does not mention in text. So without a picture, we don't know if there is one cable or two, or more, at the light location, which can have implications for how the wiring actually works.
    – Ecnerwal
    Commented Jul 14 at 22:54
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    The wiring at the fixture/s will help. Pictures showing all the wire connections on the switch you changed will help also. Using the screws on switches/outlets is usually recommended over the push in connections on the back, but should not be the problem right now.
    – crip659
    Commented Jul 14 at 23:22
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    On your drawing, we don't need to see grounds. Feel free to remove them to enhance clarity. Also, you can use white as an actual line if you use a non-white background, I like grayish green.
    – Harper - Reinstate Monica
    Commented Jul 15 at 1:53

1 Answer 1

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We all appreciate the clear photos and partial diagram, but nobody will be able to find the fault for you over the Internet. Here are some ideas for troubleshooting.

First and most importantly, none of the switches are grounded. This is a clear violation of NEC rules, and in this case an obvious danger. If I heard a pop from inside a plastic switch box and opened it to find none of the switches had a ground wire connected at both ends, I would understand this as a recipe for injury or death. Those issues need to be corrected before proceeding.

It might be necessary to map the entire circuit. This is the next obvious challenge. From the photos and diagram, we have no idea where any of those wires are connected at the other end. I'm still unclear about whether the box even has 6 or 7 cables inside.

The "surge protector" is an oddity to me. I don't understand why it's there, so I would test it for resistance to make sure it's not shorted end to end.

Next, I would disconnect all the new lights and the new switch from the circuit. Using a multitester, make sure the voltage between ground and one of the switch wires is near 120 vac. Make sure the ground to the other switch wire is near zero (may give random low readings without a load connected). Make sure both of the wires at the ceiling are not live.

Check the resistance across the two pigtail wires that go to the new lights.

With all of that sorted out, it should be a simple matter of carefully reconnecting the switch and testing its function at both ends of the load cable before reconnecting the lights.

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