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Old 02-06-2012, 03:45 PM   #1
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3 way switch replacement in 1923 old house

Hi everyone and thank you for giving a try on my problem
I would like to replace a 3 way switch with a motion sensor 3 way switch.
Situation: At my house entrance there is a electric box with 2 switches. One is a regular switch for the outside light. The other is a 3 way switch for our foyer light. This 3 way switch can be operated from the second floor at the end of the stairs. I am replacing the 3 way switch downstairs. As I opened the electric box downstairs, and pull the switches out I can see two cables with two wires each (one darker than the other). One dark wire is connected to one connection of the 3 way switch and also to one connection of the simple switch. The companion lighter wire is another connection in the 3 way switch. The other cable's wires are connected as follows: The darker wire is connected to the simple switch and the lighter wire to another connection in the 3 way switch.
It is working fine with the old 3 way switch. I can't figure out how to connect the wires to the motion sensor switch. Kindly advice.
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Old 02-06-2012, 05:04 PM   #2
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The appearance of the wires as you diagrammed them plus you mentioned the year 1923 suggest to me that the wiring is of a much older arrangement that is no longer legal. A much cleaner install would be had by stringing all new wires, exactly what would be needed would depend on how the lights are wired now. Most likely you will need a new 14-2 Romex cable from the breaker panel to the box you have diagrammed, a 14-3 cable from that box to the second 3 way switch box, and a 14-2 cable from the second switch box to the light.

If I wanted to analyze the wiring just for fun I would ask questions like:

1. Which wire is the power feed from the breaker panel? (Using just a voltmeter it will require some intuition although if you also have a long wire connected to the neutral terminal strip in the panel and stretched upstairs and across the floor this will make it easier. Either way you will need to make more than one measurement and do measurements with the switches in different positiosn.)

2. Are you sure you diagrammed the wires correctly?

3. Are there more wires with caps on them at the back of the box?

4. How is the other switch for the 3 way light wired up?

5. Which terminal of the 3 way switch is the common terminal? (Often stained a slightly darker color or having "C" engraved on the switch body near it.)

Note: Do not take things apart without labeling the various wires as you take them off one at a time. Otherwise you can make the project much more complicated.

I am only wildly guessing that wire 1 is the neutral, wire 2 is the power feed, wire 3 goes to the 3 way light, and wire 4 feeds switched power to the outside light. If so then wire 2 would be connected to black of the detector, wire 3 would be connected to yellow of the detector, nothing would be connected to red of the detector, and you would fasten green of the detector to the (metal) box. The setup will work only if the "other" 3 way switch is in one position and a second detector cannot be put there. Do not try to connect up the motion detector without knowing exactly what each wire in the wall does otherwise you can fry the motion detector.


The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.

Last edited by AllanJ; 02-06-2012 at 09:20 PM.
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Old 02-06-2012, 05:41 PM   #3
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Looks like you have what is called a California 3 way. I don't think you can make that switch work in that setup.

3 way switch replacement in 1923 old house-california-3-way.jpg
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Old 02-06-2012, 08:42 PM   #4
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That old of wiring was probably originally knob & tube.

They used the nuetral wire to go down to their switches.

That switch with sensor won't work, as Joed said

Don't get the common wire mixed up. It's VERY hard to try and figure out what they did back then.
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3 way switch , motion sensor , old house

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