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I have power coming into box from black and white wires. When wiring black to light switch and white to white leading to fixture, the breaker goes every time. When wiring the two whites together with power on, there are sparks. What am I doing wrong?

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    A picture of what you're doing would be helpful. But I suspect you're wiring the switch so that when you turn it on you are generating a short that trips the breaker. – jwh20 May 7 at 17:09
  • The white (neutral) wire in a lighting circuit shouldn't have power (should not spark) unless the light switch is on. This means you are misunderstanding something, or a wiring connection somewhere else is not correct. Pictures could help. Was the light fixture recently replaced? – JPhi1618 May 7 at 17:15
  • I can’t send picture right now. But, it’s your basic light switch configuration. Two Paris of black and white coming into box. We bought the house recently and the light that switch controlled didn’t work, when I took the faceplate off the switch and pulled it out, it wasn’t wired. I wired it: the black and white that was providing power - I connected the black to the switch. I connected the white to the white that is wired to the light. The black to the light, I wired to the switch – Sean May 7 at 17:27
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    Having a switch in a box that isn't wired up is a sign of trouble. It probably means that something else is wrong and the last person couldn't figure it out. I'd also take down the light and see what's going on up there. – JPhi1618 May 7 at 17:31
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    Can you post photos of the insides of both boxes please? – ThreePhaseEel May 7 at 23:10
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First working with power on is wrong, I am an electrician and rarely do this , if I do I usually wear hot gloves and other safety equipment. If the hot is coming in to the switch box the whites should be tied together then the black hot to the switch and the black to the lamp on the other side of the switch. With the white wire sparking and either the black disconnected or switch turned off you may be working on a switch loop, look in the box at the light and send us a clear photo of those wires if more than 1 set going to the light, especially if you see a black wire connected to a white in the box and we can provide better help. I would also change the lamp, I have had incandescent lamps internally short and trip a 20 amp breaker when turned on, but if you have a hot white wire it may be a switch loop so we need to figure that out.

  • Ed - I haven’t been working with power on, I did it once to test the connection. My gut tells me previous person didn’t wire the right color wires (switched black and white). I did change the light (it’s a wall mount light). It’s wired correctly. Black to Black. White to White. I’m sorry, I can’t send a picture right now. – Sean May 7 at 17:33
  • With lights there is something called a switch leg where white is the always hot and black is the switched hot, just want to make sure what we are dealing with here. If only the 1 cable at the light and your hot at the switch black hot on switch and light hot on switch should be correct , try changing the lamp if it trips I have run into this a few times over the years for customers and at my own home. When you said you changed the light was it the fixture or just the lamp, try removing the lamp and turning it on if it still trips you may be correct that hot and neutral are reversed. – Ed Beal May 7 at 18:30
  • Thanks, will remove the light and see if it works or not and will then see if hot and neutral are reversed – Sean May 7 at 21:13
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    It's quite possible that you have power coming two directions, from what you have described - i.e. you have a line coming into the switch box, but you ALSO have power coming into the light fixture and a switch loop running to the switch box. Possibly on different breakers! Be careful, something is not right here. – Ecnerwal May 7 at 21:41

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