3-way switch snafu??

Old 07-05-04, 06:28 PM
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3-way switch snafu??

I've just replaced some old switches around the house, including two 3-ways. Now they're not working as they did before. I've looked at different DIY sites, and they don't address problems. Anyway, one switch now works fine, and the other switch only works if the first switch is on. I've taken both apart a couple of times, to see if I did something wrong - and yes, I did hook them up as they were before. I don't want to put the old ones back on, because they're prehistoric ceramic! I appreciate any tips you may have...
Old 07-05-04, 06:57 PM
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We see this problem here once a week. You misidentified the "common" on one or both of the switches. If you relied on screw position when you moved the wires, then you used an unreliable algorithm. For example, the common on the old switch might be the lower left screw, where on the new switch it might be the upper left screw.

If you did use screw position, and if you still have the old switches, then you can identify the "common" on both the old and new switches (usually the black screw), and this should guide your correction. Otherwise, you can just use trial and error. It will take at most nine tries (each of two switches has a choice of three wires for the common screw).

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