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Junction box has two white wires and a ground, light has one white & one black


MichaelChang's Avatar
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02-12-17, 02:29 PM   #1 (permalink)  
Junction box has two white wires and a ground, light has one white & one black

Trying to replace the old ceiling light.
The light can be controlled via two separate switches at opposite ends of the room.
The old light (pictured) has two wires that go to the two white (assuming hot) wires coming out of the junction box.
It also has a thin gray wire that connects to the fat wire nut.

The new light however, doesn't have a thin ground wire and also has a black and a white.

Is this connectable (and if so, how?) or do I need to return it and get a new light that has two hot wires and a separate ground wire?

Attachment 77147


Last edited by PJmax; 02-12-17 at 04:03 PM. Reason: cropped,enhanced,reoriented pic
 
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02-12-17, 02:44 PM   #2 (permalink)  
I believe someone wired a white wire from the switch loop to the lamp, which is incorrect. Look inside the box and see if a white wire is nutted to a black one. That would be your hot wire and would be connected to the smooth zip cord wire. If the wire is not nutted, then you would have to separate the wires, and check each wire to ground to see which one gave the 120 volt reading.

 
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02-12-17, 02:52 PM   #3 (permalink)  
hmm, I think I need to go find my test light for this

 
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02-12-17, 03:08 PM   #4 (permalink)  
Or your multimeter would be better.

 
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02-12-17, 04:05 PM   #5 (permalink)  
If it was wired as a switchloop..... you'd have two black wires connected togrther in the box.


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02-12-17, 05:40 PM   #6 (permalink)  
If this is cable not conduit tell us the number of 2-conductor cables (black, white) and the number of 3-conductor cables (black, red, white) at each switch box.


I can explain it to you, but I can't understand it for you.

 
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02-12-17, 05:50 PM   #7 (permalink)  
You do not need to return the new light fixture.

Also tell us the number of 2 conductor cables and the number of three conductor cables in the ceiling box for the light fixture.

Do not disconnect anything without first labeling all the wires and parts so you could put it back the way it was if needed.

 
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02-17-17, 07:16 AM   #8 (permalink)  
Chandler,

I must be slow cuz I can't figure out how to use this multimeter to simply test if a wire's live/not live ...

 
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02-17-17, 12:00 PM   #9 (permalink)  
Name:  Untitled.png
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Note: You probably have only 120 volts so you can probably use the 200 volt setting but best to start higher and go lower if needed.


I can explain it to you, but I can't understand it for you.


Last edited by ray2047; 02-17-17 at 12:20 PM.
 
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02-17-17, 12:25 PM   #10 (permalink)  
thank you, I'll try that this weekend

 
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02-19-17, 06:55 AM   #11 (permalink)  
I've attached a couple closer pics of the junction box.
There are two harnesses coming out of the junction box along with a separate green wire.
Each harness has a white wire, a black wire, and an unsheathed copper wire.
There are four wire nut groupings:

Grouping A:
- Green wire from the junction box
- Unsheathed copper wire from first harness
- Unsheathed copper wire from second harness
- Ground wire from original light

Grouping B:
- Black wire from first harness
- Black wire from second harness

Grouping C:
- White wire from first harness (produces numbers above zero on the multimeter)
- First gray wire from original light

Grouping D:
- White wire from second harness (does not produce anything above zero on the multimeter)
- Second gray wire from original light

The original light has three wires: two gray ones and an unsheathed ground wire.
The new light has two wires: a white one and a black one.

Using the multimeter test pictured two posts above, only one of the white wires coming out of the junction box produces numbers greater than zero on the meter, the other does not.

Is the new light (only one white wire and one black wire) still usable given the above situation?

 
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02-19-17, 10:39 AM   #12 (permalink)  
It's not the light fixture. It is the wiring. It really would help to have that light fixture removed so we can see all the wiring and how they are attached in the jbox. You are using a term "harness", which is not accurate. Are you talking about a "cable"? A cable has more than one wire in its sheath combined usually with a grounding wire which is usually bare. So it appears you have two cables (black/white/bare).

I hate to ask, but remove the fixture and the bracket so all that is left is the box and wiring. Don't uncap any wires.

 
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02-19-17, 11:02 AM   #13 (permalink)  
Ok... you have two cables in the box. You have two black wires connected together.
This is where the problem is and is incorrect.

Your new light will work fine.
Like Larry said.... remove the fixture.

Make sure power is off.
Pull out the black connection and disconnect the two black wires.
Turn power back on and check each pair of white and black wires for power.
Only one cable will be the power in. Mark it so that you know it.

Once you know which cable is hot..... turn the power back off.

Connect the hot black wire to the white wire of the other cable. Put the wire nut on it.
Now you will have a white and black wire left.
Connect white to white, black to black and the grounds get connected together.

This is what you have there.

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02-19-17, 01:45 PM   #14 (permalink)  
Basically it is a ritual of "doing it right". The light will work as it is wired, as Pete says, but for future use it is better to do as the diagram suggests since you have a switch loop. The white wire from the switch should have had a piece of black tape on it to designate it as the pass through for the switch loop, technically making it a black wire. You only have one neutral and it is in place properly.

 
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03-02-17, 09:10 AM   #15 (permalink)  
PJMax hit it out of the park. I did exactly that and it works now. Thank you

 
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