Installing a light fixture


Old 06-30-01, 05:13 PM
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I am remodeling my attic and have installed some extra outlets. In the process I installed two of these outlets in a circuit that was already in place. I'll describe what I mean. I have the power wire coming from an outlet into a light fixture box. From this box there are wires going to another outlet, another light and a switch. The black power wire is connected to the white switch wire and the remaining three whites and blacks are connected together in the first light fixture box. I'm trying to replace the fixture in this first box and the person who helped me wire the room connected all the whites and black together and I can't figure out which one's to connect to my new fixture. If anyone could help, I'd appreciate it.

[Edited by bfine on 06-30-01 at 11:22]
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Old 06-30-01, 08:25 PM
Join Date: Sep 2000
Location: United States
Posts: 18,497
This same mistake is reported here several times a week.
The easiest way to solve is with a voltmeter or circuit tester, but you can use the light fixture itself as a voltmeter if you have to.
[list=1][*] Turn off the breaker.[*] Separate all wires in the ceiling box.[*] Turn on the breaker.[*] Test each black/white pair for voltage. This is your line power. Call it cable "P".[*] Turn off the breaker again.[*] Turn off the light switch too.[*] Choose one of the other two cables at random. Call this cable "X".[*] Connect Pb to Xb and Pw to Xw.[*] Turn the breaker back on.[*] Test the downstream outlet for power. If it has power, then "X" must go to that outlet (if so, I'm going to relabel the "X" cable as "D", and the third cable is "S"). If the downstream outlet still doesn't have power, then "X" must go to the switch (so I'll relabel "X" as "S", and call the third cable "D").[*] Turn the breaker off again.[*] Connect Pb to Sw to Db.[*] Connect Pw to Dw to the light's white.[*] Connect Sb to the light's black.[/list=1]

I'm not quite sure whether you have three cables in the ceiling or four. If four, then you essentially have two cables "D". The instructions are similar, but if you need more exact information, post back.

Post back and let us know how it comes out, or if you're confused by my instructions.

P.S. Don't let that friend "help" you again.
Old 07-02-01, 12:41 PM
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installing a light fixture


There are four wires coming into the box. I know which one is the power wire. The black power wire is connected to the white switch wire. There is a wire coming from another light that is also controlled by the same switch and a wire coming from an outlet that is independent of the switch. My question is which black and white wire do I connect to the fixture I am trying to replace. The way you described works, but doesn't allow any wires to connect to the new light.

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