Hot Topics: Wiring New Light Switches

a new double light switch on a wooden post with no cover

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Original Post: Can't figure out how to wire new light switches

koticphreak - Member

I have a box with two really old light switches that get stuck so trying to replace them but it's a bit confusing in there. There are three sets of wires coming in to the box, each set has a black, white and ground.

The two old switches were wired this way: Switch 1 had 2 of the black wires going to it. Switch 2 had a black and a white wire going to it. The remaining two white wires were wire nutted together and all of the ground were together.

My new switches I'm trying to install each have a black, white, red, and green and says that the neutral is required for these switches. How do I make this work???

Thanks in advance!

lambition - Member

The switch that had both black and white wires going to the switch is a switch loop. It has power at the light fixture, then it is controlled by feeding power to white wire and switched power back on black wire.

In this case, you normally don't have neutral in the junction box and cannot use a smart switch requiring a neutral wire.

However, in your case looks like your other switch is not a switch loop and actually has a neutral. It is very likely that switch 1 and switch 2 is fed by different circuit (breaker) and you cannot connect neutral from two different circuits. So, you will have to rewire wiring at the light fixture controlled by switch 2 so that the light is powered from circuit feeding the switch 1.

Some pictures of inside of switch junction box and light junction box will be helpful.

White wires wire nutted together will be your neutral, which connects to white wire from your new switch. green goes to bare ground wire. black goes to live wire, which will be one of the black wires. This is the one that is always hot regardless of switch position. You will have to figure this out with a multimeter or non-contact tester. Red wire goes to wire going to the light (which will remaining black wire.)

PJmax - Group Moderator

You are not replacing a switch for a switch, You are removing a switch and adding a smart switch. A lot of older wiring was not set up for a connection like that.

koticphreak - Thread Starter

See image. I tried to color code it.

The bright orange wires went to switch 2.

The blue are both black wires (even though one looks white) and went to switch 1.

The brownish are the two white wires that were together.

All the grounds which I did not color code were together.

light switch wiring with color code graphic squares

PJmax - Group Moderator

Can you give us a picture from a little further out.

It looks like three wires on the orange side.

On the blue side...... one blue is line...... one is load and the white splice is neutral.


We need the picture to show the switches to confirm your description.

Also, if you have a switch loop like in your description, then also need to see the wiring in the light fixture as it will require some rewiring.

koticphreak - Thread Starter

Sorry - wasn't understanding what we were trying to get to. Getting to the wiring of the light will be extremely difficult as it's very high up.

Hopefully this picture helps to elaborate on my explanation:

the open wiring behind a light switch

PJmax - Group Moderator

You can install a smart switch in the left side.

You cannot in the right side as you don't have a neutral for that circuit.

koticphreak - Thread Starter

Okay, so how can I wire it? From the new switch I have a black, a red, a white and a green.

Which of the two black ones going to the current one go to the black and which to the red? Which of the two neutrals currently together goes to the new switch?

PJmax - Group Moderator

You need a way to test the two black wires for power. One will be always live.

Black from switch to always live black wire.

Red from switch to the other black wire that is not live.

White from switch goes to the two white wire splice.

Green goes to the bare copper wiring.

joed - Member

If the light is on the ceiling (most are) then cable going out the top is most likely the light. It gets the red wire. The cable coming in from the bottom is most likely the power feed and gets the black wire.

lambition - Member

Others have explained how to wire left switch.

With right switch, you cannot wire a smart switch directly, but you may be able to just use power going to left switch instead. That will require some rewiring at the light fixture. That is why I was asking for the picture.

I also noticed ground wires are not connected. All ground wires should be connected together (regardless of which circuit it came from) and also to each switch.