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Hot Topics: Connect new light switches

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Original post: Can't figure out how to turn on new light switches

koticphreak Member

I have a box of two really old light switches that get stuck so try to replace them but it's a bit confusing in there. There are three sets of threads that come into the box, each set having black, white and ground.

The two old switches were connected in this way: Switch 1

had 2 of the black wires that would go to it. Switch 2 had a black and a white wire that goes to it. The remaining two white cables came together and the whole ground was together.

My new switches I try to install each one has a black, white, red and green and say that the neutral is required for these switches. How do I do this work ???

Thanks in advance!

lambition Member

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

In this case, you normally do not have neutral in the junction box and cannot use a smart switch requires a neutral wire.

But in your case, it looks like your other switch is not a switching loop and actually has a neutral. It is very likely that switch 1 and switch 2 are supplied by different circuits (switches) and you cannot connect neutrally from two different circuits. So you have to switch the wiring on light fixtures controlled by switch 2 so that the light is driven from the circuit supplying switch 1.

Some pictures on the inside of the junction box and the light junction box will be helpful. [19659006] White wires that are interconnected are your neutral, which connects to white wire from your new switch. green goes to bare ground wire. black goes to life thread, which will be one of the black wires. This is the one that is always warm regardless of the switch position. You need to find out with a multimeter or a contact-free tester. Red wire goes to wire that goes to light (remaining black wire.)

PJmax Group Moderator

You do not replace a switch for a switch, you remove a switch and add a smart one switch. A lot of older wiring was not installed for such a connection.

koticphreak Thread Starter

See photo. I tried to color the code.

The bright orange wires went to switch 2.

The blue are both black wires (although you look white) and went to switch 1.

The brown ones are the two white cables that were together.

All the basics that I didn't color code were together.

 light switch wiring with color code graphic boxes

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 …… a blue is line …… one is load and the white joint is neutral.


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

If you have a switching loop as in your description, then you must also see the cables in the lamp as it will require some wiring.

koticphreak Thread Starter

Sorry – didn't understand what we were trying to get. Getting to the wires of light will be extremely difficult as it is very high up.

Hopefully, this image will help prepare my explanation:

  The open line behind a light switch

PJmax Group moderator

You can install a smart switch on the left side.

You cannot on the right side because you do not have a neutral for that circuit.

koticphreak Thread Starter

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

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

PJmax Group Moderator

You need a way to test the two black power lines. One will always be alive.

Black from switch to always live black wire.

Red from switch to the other non-live black line.

White from switch goes to the two white thread joints. [19659006] Green goes to the simple copper lines.

joed Member

If the light is on the ceiling (most are) then the cable that goes out on top is probably the light. It gets the red thread. The cable coming in from the bottom is probably the power supply and gets the black line.

lambition Member

Others have explained how to connect the left-hand switch.

With the right switch, you can't plug in a smart switch directly, but you might just be able to use the power to the left switch instead. It will require some wiring on the lamp. That's why I asked for the picture.

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

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