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Question DetailsAsked on 6/27/2014

I am changing a light switch and the power has two black and one red wire. I am not sure what wire is neutral?

My new switch has two black wires and a green wire.

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3 Answers


Is this a photosensor or such that gets cut into the feed line to control the lights or device ? OR maybe a three-way switch, though it should have 4 wires total in most cases - black, red, white, green (or three wiresplus ground screw).

Should have been an instruction sheet in the packaging too which might clarify matters, showing different ways to wire different things.

I am not confident you have the right switch - the feed sounds like a three or four-way feed with the red wire, or possibly a photocell switch feed, but the switch sounds like a standard one-way (single switch controlling those lights), which has no neutral - it just interrupts the live (black) feed to turn light on and off, plus the ground to ground the switch to the box I am actually pretty certain you have the wrong type switch - compare to the one that came out - it probably has three live wire connections plus a green ground screw.

Perhaps if you could provide (using the Answer This Question button right below your question) the make and model number of the switch, and a description of what it is controlling and where the switch is going, and if this is a three-way or 4-way switch circuit (3 or 4 light switches controlling the same lights from different places in the house), we can help you. A photo of the back of the switch would help too - attach using the little yellow icon above the answer box.

Answered 5 years ago by LCD


If this switch is a dimmer it sounds like someone replaced a three way switch with a single pole switch. The reason I ask is it a dimmer is that usually in residential controls the regular switches have screws to connect the house wiring to. Many dimmers use pig tails, or wires comming out of the swich to connect to nowadays. You should have a power supply black or feed and a load black in the box.

You are not the same person that posted a question about GFCIs just a minute ago are you? If so it sounds like you had someone working on the wires that have things messed up a bit. If it was once a three way the red wire should have been painted black or had black tape on it to identify it as such. I just worked on a kitchen that had me scratching my head because someone replaced a threeway with a single pole switch and pushed the common wire so far in the box that I could not see it. Once I did I found out what the mystery switch was in the house that did nothing.

As LCD said a picture would help to answer this, And actually if you are a DIY a picture before you pull apart something is a great idea.


Answered 5 years ago by ContractorDon


I think Don is onto something here - I am so glad when he covers for my ovesights. I totally spaced on the pigtail thing - so we are both on the same thought about it possibly a three way or three-pole switch and your new one is single-pole.

(FYI in case terminology is getting to you here - 3-way or 4-way means either 2 or 3 different switches at different places control the same circuit - commonly at opposite ends of a large room, or top and bottom (and maybe middle of split-level landing with 4 way) of stairs. Single-pole means a single switch with one setting - on or off, for one item. Two-pole would normally mean Item 1 (maybe light) on, Item 2 on (maybe fan), or both off. Three-pole would normally be Item 1 on, Item 2 on, Item 1 and 2 on, or all off at the four settings. Just to make it more confusing, people tend to interchangeably uses the terms "way" and "pole". Also, "pole" and "throw" are interchangeable.

Another possibility comes to mind - especially if a dining room or high ceiling living room or such - one of the box blacks may be incoming live (to connect to the switch), one the live wire out from the switch to the light, and the other (red) live from the switch for a fan - the black and red outbound leads both going to the same place but one for fan, one for lights. White presumably is spliced white to white and tucked back in the box somewhere.

If you did not disconnect the red wire from the original switch - only a black, and you only have a light or a fan but not both, the red may be from when it had a fan and light both (or was at least wired for it) and used a 3-pole switch but unused now.

Confused yet ?

As for the photo - if available- need one of both new and old switches, or make and model number of each, identifying which is old and which is new.

Answered 5 years ago by LCD

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