3 way switch replacement problem.

jeremycmMay 24, 2011

I have two lights connected to two 3 way switches. The one at the bottom of the stairs was old, probably original to the house so I decided to replace it.

Knob and tube wiring, not really color coded but two attached to the right look somewhat red and also seem to come into the box together, left one from a seperate spot. Both old and new had one screw on left and two on right. New was black on the bottom right and brass for the top two. I connected new just as old was and now if the top of stairs is up the bottom switch turns it on/off but if the top of stairs is down the light is always off.

I'm thinking either I didn't transfer the wires correctly or the common is different? Can I just try to switch which one is common? There are only two other options.

I have a multimeter with two probs but I'm not that experienced with electrical. I've read other posts but have just gotten confused, which is why I'm thinking to just rewire until it works.

Thanks for any suggestions!

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normel

Try connecting the two that come into the box together to the two brass screws.

    Bookmark   May 24, 2011 at 1:24PM
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linesman

Hello jeremycm

If you don't feel safe useing a meter, you can use the following.
wireing combinations

Here are the 9 combinations you need to check:
Switch #1, wire "A" to common. Switch #2, wire "A" to common.
Switch #1, wire "A" to common. Switch #2, wire "B" to common.
Switch #1, wire "A" to common. Switch #2, wire "C" to common.
Switch #1, wire "B" to common. Switch #2, wire "A" to common.
Switch #1, wire "B" to common. Switch #2, wire "B" to common.
Switch #1, wire "B" to common. Switch #2, wire "C" to common.
Switch #1, wire "C" to common. Switch #2, wire "A" to common.
Switch #1, wire "C" to common. Switch #2, wire "B" to common.
Switch #1, wire "C" to common. Switch #2, wire "C" to common.

Hope this helps

Have A Nice Day
Linesman

    Bookmark   May 24, 2011 at 2:09PM
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bus_driver

For the lesser experienced, hooking the wires at random on a three-way switch has a one-in-three chance of being correct. Moving all three wires one position clockwise on the switch brings the chances to two-in-three. Moving all clockwise again for the second time exhausts all the practical possibilities. One of those will be correct.

    Bookmark   May 24, 2011 at 5:21PM
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wayne440

An elegant solution, thanks.

    Bookmark   May 24, 2011 at 5:37PM
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brickeyee

"Moving all three wires one position clockwise on the switch brings the chances to two-in-three. Moving all clockwise again for the second time exhausts all the practical possibilities. One of those will be correct."

And as long as the load is present (light fixture) all that happens is the switches fail to operate correctly.

    Bookmark   May 25, 2011 at 4:28PM
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