Replacing old switches


Old 05-24-07, 11:24 AM
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Question Replacing old switches

I recently painted my house and this pointed out the need to change out the old switches that have been in place for 20 years. Not all of the switches needed to be changed because some were newer than others.

One of my hallways has 2 light fixtures controlled by 3 switches. Only one of the switches, the one at the end of the hall, which is a 3-way switch, needed to be changed. I bought a new 3-2ay switch and wired it in. It will work, however, only when the other two switches are switched a certain way. And if I get this new switch to work maybe one of the other 2 may work, but not all three. Depending how the switches are arranged determines which switch will control that light at that moment.

Why is this happening? Do I need to replace the other two switches?
Old 05-24-07, 12:15 PM
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If the old switches worked properly, then you wired this wrong.

Did you make sure to put the common wire on the common terminal and the traveler wires on the traveler terminals?

Another possibility is a bad switch, but that is not likely.
Old 05-24-07, 01:01 PM
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Moving wires from the old switch to the new switch by matching screw position is not a reliable algorithm. You need to move the wires by matching screw color. If you still have the old switch, you should be able to use it to figure out your mistake. Otherwise, you can solve this by trial and error. Since the only thing that makes a lot of difference is which wire is connected to the black-colored screw, it shouldn't take more than three tries (i.e., two more tries).
Old 05-24-07, 06:29 PM
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Your new switch has one screw that is black. This is the COMMON screw. Put a different wire on the common screw and try again. If you are lucky it will work. If not then put the last wire on the common screw and it will work. The other two screws don't matter.

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