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Let me caveat by saying that I am a new homeowner with relatively little electrical experience, so please bear with me...

Our house has a standard 3-way switch with the light between the two switches. Originally I wanted to convert the 3-way to function as two single pole switches. I would have to add more wire directly between the switches to make that work, so I'm trying for a simpler option. Essentially, I want to splice an additional light onto the second switch, to work in tandem with the light in the middle. (see diagram)

Additional light on end of 3-way switch

The 3-way switch is working fine, but the new additional light turns on for a second and then off. First, does this setup work? If it does, does anyone have any ideas why the light is turning on then off immediately?

  • Those lights are in series, the black and white in the center light, should also be the same wires going to the lose light – noybman Sep 5 '17 at 5:15
  • To make it more clear - pull the new wires for the added light from the electrical box that current light is attached to instead of the end of the line switch box. Put the wiring in that switch box back the way that it was. – Michael Karas Sep 5 '17 at 12:29
  • As far as on and then off immediately, I assume you're using an LED or CF bulb? It's not getting enough power for its electronics to work so it turns off. – JPhi1618 Sep 5 '17 at 17:35
  • Thanks for the clarification regarding a circuit in series versus in parallel. I suppose I should have paid more attention in Physics 122... – White Fish Sep 7 '17 at 3:06
  • @JPhi1618 Yeah, I was using a CF bulb, so that must be the case. – White Fish Sep 7 '17 at 3:07
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Ok In Tandem so when either switch turns the lights on or off you want the additional light on .. Simple

See those black and white wires that go to the light fixture in your current Original Lamp Fixture .. Wire your new lamp socket right there a black wire to the black and a white wire to the white and your green wire to the fixture ground (green wire) my drawing does not show the ground wire to the additional fixture but make sure you use it! BTW leave your switches alone ..

Done..

Tandem Light

EDIT 8 Sept 2017

Make sure you turn your Circuit Breaker off before working on it (TEST that the breaker is off by operating both switches to see if your original light turns on - test with a multimeter to verify that there is no power between white and black on your original lamp), wear some electrical gloves and use the one hand rule - you will be safe that way. I work on circuits AS IF they were LIVE circuits - protects me from my forgetfulness .. or any special surprises. You will need wire nuts (yellow - maybe red) to attach the wires. Black to Black, White to White, and [Green/Copper] to [Green/Copper].

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  • Thanks for the diagram. So it appears there is no way to make this work without running some wire directly from the existing light to the new light. Correct? – White Fish Sep 7 '17 at 3:02
  • @WhiteFish you have to have wires to the light anyway. the easiest way is to run the wires, it is not that hard to do. Just some romex some staples to staple it down and your light fixture box. Note my additional edit - for safety and connection info. – Ken Sep 8 '17 at 19:11
  • Thanks! Next time I'll plan it out before I drill holes and run cable from the second switch to a new light! – White Fish Sep 11 '17 at 5:38
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Good grief, nobody could expect to understand that tangle of red, black and white. Let's get some red and purple tape and actually mark the wires for what they do.

enter image description here

Well that's a lot better.. White is actual neutral. Black is actual hot. Red is switched hot. Purples are 2 messengers - they're the same, so there really isn't any need to distinguish them from each other.

I didn't color your extra wires. Can you see a bit better how this is going to work -- or to be more precise, not work?

The original lamp is getting its switched-hot filtered through another lamp. This is called putting them in series. They're not designed for that.

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  • Other than the incorrect modifications to the original picture posted, it was spot on for layout and colors all the way down to the "signal tape". Unfortunately your teaching aid here has a slight oops in description because not only is BLACK hot, but so is the purple "signal" color. The key mistake in his edit was that he turned it into a series circuit. I should have made a visual edit. Therefore, OP, please wire your new lamp so that it is using the same wires that goes to the center light via pigtails and hook the right hand switch up the way it was – noybman Sep 5 '17 at 23:40
  • The purple does make the 3-way switch functionality more clear - the red, black, and white on 3-ways does get confusing... Thanks for clearing up the issue! – White Fish Sep 7 '17 at 3:11
  • @notbman Messengers are considered hot, and purple means hot. In conduit you could use actual purple THHN but in Romex you must settle for taping it. You could use any hot color other than white red black. Legal hot colors are black brown red orange yellow blue purple pink. – Harper - Reinstate Monica Sep 7 '17 at 8:22

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