Confused Wiring

I have a light fixture w/ 3 way switches. I am replacing the fixture. All the blacks come out of the cables and connect except one. One this cable it is reversed and the white is hooked to the hot and the black is loose. Is this the switch wire and should it go to the white.

thanks for the help

32 cent

 

You may need to give more info? At times the white is used for a hot wire, but it should have some black tape or black marker on it to say it is hot. Is there a three wire going to the light fixture (white black red)? At the three way sw. You should have one hot and two travelers that go up to the light fixture. You may have to ohm out the wires to find out exactly what you have.

 

I opened up the switch plate and it has a red wire so i guess it is 3 wire, but up at the fixture it is only black white and ground.

 

Generally, the correct advise is to connect the new fixture just like the old one was hooked up...unless there's some compelling reason to think the old wiring was wrong.

Your description does not tell how many cables (romex) come into the box or how many wires each cable has. There's gotta be at least two up there, and we'll talk about them. I'm assuming you have not taken everything apart, but have just removed the fixture.

If you have a white wire from one cable (Cable A) connected to a black from a different cable (Cable B), and the black from that first cable (Cable A) is the loose black, then chances are Cable A is a "switch loop"...the white from Cable A takes power to the switch, and the black brings it back. If there are multiple switches involved, there will be three wire cable (blk/wh/red) going between switches.

Now, in what I described, Cable B is the incoming (unswitched) power. There ought to be a loose white wire from it...thats your neutral. Connect it to the fixture along with the black from Cable A. All grounds should connect together...

 

It sounds like you know my problem because you are describing it. I have 4 cables coming into the junction. All blacks and whites are hooked up to each other. Except the one cable where the white runs to the hot(black wires) and the black coming from that same cable is the loose wire. In other words no other wire is loose. It confuses me that the one white one goes to the hot(black) and the black is left loose. I am only to assume what you said that the white is used as a switch wire and the loose wire is to be hooked to the white wires to complete the circuit.

correct??

 

You have a switch loop. It is wired correctly. Connect your new fixture to the same two wires as the old light fixture. In a switch loop the power goes to the switch on the white wire and comes back on the black wire.

 

no, don't hook the black to the whites to "complete the circuit"...the new fixture "completes the circuit". You are putting in a new fixture, right?


OK, so there's four total cables. Sounds like the box is just acting as a junction box..the extra cables are likely just feeding other boxes (call them Cable C & D). Does this describe the box?:

Wirenut 1: cable B, C, and D blacks with Cable A white (as was mentioned before, this white should have been reidentified as a hot wire with electric tape, magic marker, or other method, but this often does not get done)
Wirenut 2: Cable B, C, and D whites plus either a white pigtail, or the old fixtures white wire once connected there

Loose: Cable A black (and possibly a white pigtail)

The Cable A black used to connect to the old fixtures black wire, right?


If this is the scenario, hook the new fixtures black to Cable A black, and the new fixtures white in with the whites with Wirenut 2 (or, if there's a pigtail off wirenut 2, just connect the new fixtures white to that).

 

Well, that is how I knew there was a problem. I connected the new fixture black to the loose wire black and the fixture white to the whites and it would not turn on. That is how I discovered I connected the fixture black to a non hot black wire.

32

 

the 3 wire you see in the switch box runs to the other 3 way(or should) those are your travellers. if i read correctly, it sounds like you have 3 cables that are hot feeds in your lighting outlet, and the 1- 2 wire carries the feed and switch leg to 1 of your switch boxes therefore probably dead ending the other(1 switch box should only have a 3 wire in it with all colors to the switch, the other switch box should have a 3 wire and a 2 wire) one of the legs of the 2 wire in the switch box should be tied to one of the wires of the 3 wire cable going to the other switch