Basic Light Switch Wiring--Help!

I think a made a big goof!
I was trying to wire a light switch to an existing ceiling light fixture (pull string) in an unfinished room. All I did was run the standard 12-2 wiring from the new switch box up to the existing fixture. Then I drywalled everything up. I went to wire the switch box line up with the existing wiring that leads to the fixture. When I turned things on it tripped and won't properly work from the switch. The pull string works fine (off and on), but when I try using the switch it trips that circuit.
WHERE I THINK I WENT WRONG: I now think that I was supposed re-direct the existing power that ran to the existing fixture in the ceiling down to the new switch location. Then run a separate line of 12-2 from the new switch location up to the light existing light fixture. Am I right? If so, is there a way to rectify this without ripping out the drywall to have the switch and fixture work properly?
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041115 1606 - Cabrzama posted:

Take a look at this...
http://www.electrical-online.com/howtoarticles/lights.htm
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at the existing light you had one black wire and one white wire attached to the fixture. First , leave the white wire on the fixture. Second, splice the black wire formerly on the fixture to the white wire going to the switch. Third, attach the black wire coming back from the switch to the fixture. Last, connect both wires to switch terminals , doesn't matter which way

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"Roy Mottola" wrote

one little refinement would be to wrap a band of electrical tape around the white wire going to the switch - this indicates that the white wire is part of the hot side of the circuit. obviously this makes no functional difference, but someday, someone (maybe even you!) will want to make some other alteration in that j-box and this little flag will be a signal about what's going on!
so you know, it is generally considered good practice to locate the switch on the hot side of the circuit, i.e. current hits the switch before the fixture - just as you describe in your "what went wrong" paragraph. it is almost always possible to do this, even when retrofitting existing wiring. the reason that this is desirable is that it adds an extra level of safety - if someone is working on the light fixture, for example, and accidentally turned off the wrong breaker, there is some chance that they will avoid a shock because the circuit (in the wire that is actually connected to the fixture) is broken (by the switch being in the off position). no guarantees, but at least it reduces the number of ways you can create a short circuit if you made a mistake somewhere else.
oh, and remember to leave the pull-cord in the "on" position once you re-wire. :-)
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Cabrzama wrote:

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willshak wrote:

Nice presentation willshank.
But, how come you didn't even mention a ground conductor?
Decent toggle switches have grounding screws on them:
http://www.leviton.com/sections/prodinfo/newprod/npleadin.htm
I think that if this newsgroup is going to advise a newby on something as simple as this subject, then we ought to give him a more complete education.
The 12-2 he says he ran should have a ground conductor in it and be connected the the ground conductors in the box the existing ceiling fixture, the other end of that grounding conductor should go to the grounding screw on the switch, and if there isn't one on the switch itself, then to a metal box if the switch is in one or at least under one of the switch frame's mounting screws.
What say?
Jeff
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Jeff Wisnia wrote:

I did say.... "Only the black and white wires are shown for clarity. All ground wires must be connected to each other" I assumed the OP just made the wrong connections in the fixture. It was whipped up in a hurry just to show the black wire connections.
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willshak wrote:

Apologies, you are correct. I zipped right over those words without them registering when I looked at your excellent little diagram.
But, if I missed it, maybe the OP could have too. <G>
Jeff
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