Question: 2-way switch used with 3-way setup !?

[mathieu.lalande]

Hello,

I just upgraded the swtich for my diner table light.

This light is controlled by 2 switch, one in the hallway and one dimmer from the wall in the room itself.

When I took the switch out I noticed that the one in the hallway is a

3-way type (3 wires) but the dimmer has only 2 wires.

How can that be ???

I installed a new 3-way dimmer where the 3-way switch was and a new 2- way switch where the old dimmer was.

Of course, everything still works since I did not play with the wires setup.

Any info would help ...

Thanks !

[Doug Miller]

As you describe it, this is impossible. Therefore your description is incorrect in some respect.

"Everything still works" meaning... ? If by that you mean it still works as before, I can believe that. If you mean that it did work, and still does work, as though you had a three-way switch at each location, sorry, I don't believe that.

Try this: a) Turn the light on at the dimmer. b) Now turn it off with the switch. c) Try to turn it back on with the dimmer. If you've described the situation correctly, you can't.

[mathieu.lalande]

Doug,

That's exactly what I tought when I saw the setup. I am no electreician but I have changed a few switch/dimmer before.

Could there be an unused wire I don't see. Is that possible ?

Exactly, the switch HAS to be ON for the light work. Is the 3rd wire from my dimmer stopping at the light fixture ?

Again any info would help ...

[Doug Miller]

Yes, that's possible.

It's also possible that the whole setup was wired by someone who didn't understand how 3-way switches work.

It's hard to say where it's going, without seeing it.

In order to control one light independently from two different places, you need a 3-way switch *and* three wires in each location. If you don't have that, it isn't going to work properly. Google is your friend here; there are many diagrams available on the web showing how to wire 3-ways.

[Bill]

People don't always wire things the proper way. So yes you probably have what you have described and this is not the proper way to do things. You can of course fix it right.

Might need to run the correct wiring or have an electrician do this if you want it to work properly.

[Mark Lloyd]

I found exactly that setup in a relative's house once. This looks like it used to be a normal 3-way system, but one of those switches was replaced with a dimmer. The other switch is no longer used as a 3-way, and is just in series with the dimmer (must be on to use the light). If that is the case, you should find an unconnected wire (originally the other 3-way traveler) in the box with the dimmer.

[Jeff Wisnia]

You're correct of course in the general sense....

But there have always been more than one way to remove the pelt from a feline.

I once mounted a small 120vac coil SPDT relay with 5 amp contacts inside the ceiling box of a lamp fixture to avoid having to replace the two conductor run from a SPST switch quite a distance away.

I was converting that lamp to a "three way" system by adding a SPDT switch close to the the fixture, which made for an easy to fish three conductor run.

Because the hot feed entered the ceiling box, and not the existing switch box made that project an "easy do".

That was about 25 years ago, and for all I know it's still working fine. .

Jeff

[mm]

Though they are all pretty much the same viewed from one pov, there are a surprising number of ways to wire three-ways. Anyhow, yet, it might stop at the light fixture, or maybe it's tucked wayin the back of the box that had the two-way switch. I'm thinking it's the latter.

If so what you could do is move the 3-dimmer to where the 2-dimmer used to be, and put the 3-way back where it was.

If you really want the dimmer in the new spot, you can buy a new 3-way switch and put it where the 2-way dimmer had been.