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How do you wire a light switch to an existing light that does not have a switch?


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2015-07-15 19:16:48
2015-07-15 19:16:48

First of all, does this mean that the light is permanently on?

Basically what a switch does is interrupt the current flow going to the light. When you turn it on, it makes the connection that is already there with plain wire.

So, installing a switch involves finding the hot wire that goes to the light, cutting it, and connecting each end of the switch to each section of wire. YOU MUST DISCONNECT POWER BEFORE DOING THIS, OR YOU WILL ELECTROCUTE YOURSELF.

Also, completing a project like this in a manner that is up to code is quite a bit more complicated than my explanation. The code is there for your safety, following it is common sense. You must use an approved switch, in an approved box, mounted securely in an appropriate manner, etc. If you aren't completely sure you know what you're doing, don't do it.


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If the question is, can I wire a switch to an existing light fixture (and I must assume that it's something like a pull-chain light fixture), the answer is yes.If the question is, "how do I wire a switch to an existing light fixture that has no external switch", the answer is, "in series".The attached web site gives simple instructions on how to wire a basic light switch to an existing light.See sources and related links below

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Your question implies that you want to wire a new branch circuit controlled by a switch using the existing light fixture. DON'T DO IT! It is a code violation. The existing light has a switch already. you cannot control another light with another switch when the first light is OFF. There are safety reasons for not doing this. If you wire the new light from the hot side of the existing light, you can be shocked even if the new switch is OFF.

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Piggyback off the box for the existing light. Run a wire from the existing junction box to a new junction box (which is placed wherever you want the new fixture). Then, in the existing box, connect the wire coming from the switch, the wire for the existing fixture, and the wire for the new fixture together using wire nuts. Wire up the new fixture, and presto, you have two fixtures on a switch where there was only one before.

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If you want to control the new light off of the existing switch then connect a black wire from the new light's black wire to the existing light's black wire and the new's white to the existing lights white wire and grounds to grounds. Or if there is no existing light; connect the black wire from the new light to one terminal screw on the SINGLE POLE switch (but not the green grounding terminal) The other terminal on the switch is connected to a black, hot all the time, wire which is paired with a white neutral wire that will connect directly to the white wire on the light. Grounds to grounds. Use 14/2 with ground wire on 15 amp circuit breakers and 12/2wg wire on 20 breakers. For more about SINGLE POLE switch wiring see the attached link.

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You have to pull a new wire. There is no way to do it with the existing wire, at least no way you should do it and be in code.

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