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I have an old Slater 20a switch with 3 screws (no ground). The wires to it are one black, one red, and one white (which was spliced to an orange wire at the end for some reason). It is a 3 way switch that works the utility room light and another switch works it from the other side of the room. The positions are (looking at switch from the front) black bottom right, red bottom left, white top right. The new switch has 4 screws (plus ground of course) - black on bottom and copper on top. Where should I put these 3 wires on the new switch? First pic of the front of switch, Orange is white. Second pic of the back of switch enter image description here enter image description here

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  • Can you provide us with photos of the sides of the old 3-way switch please? – ThreePhaseEel Feb 19 at 5:22
  • Omg I apparently suck at uploading pics 🤦🏽‍♀️ – Kara Michele Feb 19 at 5:45
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    For future reference, screws can both tighten and loosen. If you'd loosened the screws, that would have left you with another inch or so of wire to work with when adding in the new switch and they'd have already had the loops in the ends so you wouldn't have to strip the and bend new ones. Just makes your life easier. – FreeMan Feb 19 at 13:37
  • I wonder if the orange pigtail on the white wire was serving the purpose of re-marking the white (normally neutral) to non-neutral (maybe one of the big dogs will clarify if that makes sense). If that is the case you might be wise to continue re-marking the white. – izzy Feb 19 at 18:38
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    Thank you so much, friends. I normally wouldn’t snip the wires. At first I thought we were running a new line down but then was informed we’re just keeping that circuit and putting in fresh switches/receptacles. But I’m so grateful for all your kind tips and suggestions. You’re all awesome. – Kara Michele Feb 20 at 21:32
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Common is the black screw. Travelers are the brass screws.

And position does not matter at all on a 3-way switch. You can buy 6 different brands of 3-way switch out of the bins at Home Depot and find 6 different positionings of those screws.

3-way switches have 3 screws + ground

A switch with 4 screws + ground is the wrong switch.

If it is a "4-way switch" (2 brass 2 black), by good fortune, you can wire it exactly the same way - 2 travelers on brass and third wire on one of the black screws. Normally these things matter, but it happens to work out with 4-ways that it doesn't matter which black screw. However, only use a 4-way for a 3-way if you enjoy paying $10 for a switch instead of $2.

If it's a "smart switch", lighted, motion sensor etc., then it's more complicated. You need to study your 3-way layout carefully and figure out where in the circuit it's possible for it to go. At that point we'd need photos of the wires in the backs of the boxes, without anything disconnected (photos of a bunch of loose wires splayed out in every direction are worse than useless, and destroy the necessary information of "how it was connected before").

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    Wow you all are awesome! I love this site. Thank you so muuuch!!! I’m just getting back to the project today after a couple shifts of (my regular) work so I’ll report back my assured success later! – Kara Michele Feb 20 at 18:46
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Leviton is a manufacturer. They make all kinds of electrical equipment, including both simple and smart switches. If you are installing a smart switch of any type (timer, WiFi, remote, etc.) then we'll need to know the model # and possibly additional specifics to get this figured out. But assuming it is a simple 3-way switch replacing the existing switch, this is straightforward.

As noted in comments, you should always remove wires that are screwed into a device using the screws rather than cutting the wires. That being said, you have one advantage over some other questioners: you know 100% for certain which wire was connected to each screw!

The trick with replacing 3-way switches is figuring out which screw terminal is for which function. There are (excluding ground) 3 connections:

  • Common = Hot or switched hot - The actual function depends on whether this is the first or last switch in the series of panel -> 3-way switch 1 -> (possibly 4-way switches) -> 3-way switch 2 -> light (or other switched device).
  • Travelers - There will be two of these and they are functionally identical.

The screws can be configured "any which way". Typical would be "common on one side, travelers on the other side" or "common on top, travelers on both sides on the bottom", but technically anything is possible. Fortunately, it is easy to figure out:

  • Beg/borrow/buy a multimeter if you don't already have one.
  • Set it to resistance or, as most have, continuity testing mode. Depending on the model, continuity testing may be combined with the any/all/lowest resistance (Ohms) mode.
  • Check continuity with each pair of screws. Flip the switch. Check continuity with each pair of screws. If your multimeter beeps for continuity (technically, resistance below a very low threshold) then you can do this without even looking at the meter.

You will find that one screw is part of a continuous pair no matter which way the switch is flipped - that is common. The other screws are each part of a continuous pair only in one switch mode - those are travellers.

On the new switch, you can do the same testing, but it is easier to read the instructions. In addition, most new switches will have different color screws (e.g., black, brass or silver) - the two screws that are the same color will be the travelers and the other screw the common.

  • Connect the old common wire to the new common screw.
  • Connect the old travelers to the new traveler screws.

That just leaves ground. Most new switches will have a ground screw. If you are using a metal box and the switch has a metal yoke then physically installing the switch (provided there is no paper, paint, rust, dirt, etc. blocking solid contact between yoke and box) takes care of ground. If not, if you have a ground wire available in the box then you should connect it to the ground screw. And if you don't have a metal box and you don't have a ground wire available then, as I understand it, for simple switches (smart switches might need ground) you can ignore that ground screw.

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    Commented below to both of you who answered. Not sure if I need to comment on each answer or not. (New here) But just in case, THANK YOUUUUU! Reporting back later today with success! – Kara Michele Feb 20 at 18:48

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