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I have replaced both my 3 way switches but only one works correctly. I was told by the local hardware store that you wire each switch the same. red and black on top on the brass screws. and the white one on the black screw only the 1st switch works correctly. if I try to turn the light on from the other switch it won't work without the other switch on. if I have both switches off, the 2nd switch won't work at all. also there doesn't seem to be a ground wire for these switches

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Well that is close but today the common screw is one color and the other travelers are the same but different color. The store's advice can be right but I have also run into this on switches that were not labeled or color coded. The good thing is it won't hurt anything if the 3 wires are mixed up. If they don't work correctly you can try moving the wires to different screws 2 at a time only a few trys at worst case and it will work correctly I have had to do this for friends that messed up switches and over for dinner was asked for help with no meters or testers and just a screwdriver.

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That's completely wrong. They have the right idea about the 2 brass screws vs. the 1 black screw. The 2 brass screws are the 2 travelers, and they are interchangeable.

But there is literally, seriously, no color code whatsoever for 3-way switch wiring. The travelers might be black-red, might be red-white, might be black-white. You do not know.

Also the positions of the screws are different on every switch. Maybe on that particular one, the travelers were on top, but the next one, they'll be cattycorner.

That's why I mark the travelers yellow using colored electrical tape. (They are interchangeable).

How do you find them? What is true is that both travelers will always be in the same cable. That's not always helpful, but it will be true at at least one of the switches. With luck the travelers will be the same colors at both switches, but that is not guaranteed. I have seen 3-way wiring diagrams where the colors change 3 times in the same circuit! (Diagram #4 here).

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    So easy now to take pictures of the original switches with wire positions before changing anything... – Solar Mike Mar 21 at 5:48

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