Results 1 to 10 of 10

Thread: 3 way switch wiring question-SOLVED

  1. #1

    3 way switch wiring question-SOLVED

    I hope this is the right forum. I wasn't sure. This is for switches at top and bottom of the stairs in my house.

    I have 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 like I thought 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 information online but have just gotten confused, which is why I'm thinking to just rewire until it works. Thanks for any suggestions!
    Last edited by Jeremy Milam; 05-24-2011 at 7:54 PM.

  2. #2
    Join Date
    Feb 2003
    Location
    McKean, PA
    Posts
    15,593
    Blog Entries
    1
    First off, you really need to replace the knob and tube wiring, it is a fire hazard. The age of the wire is such that just working on it can break the insulation leaving the conductors exposed.


    If you examine the diagram below you should be able to figure out which wires to swap.
    Lee Schierer
    USNA '71
    Go Navy!

    My advice, comments and suggestions are free, but it costs money to run the site. If you found something of value here please give a little something back by becoming a contributor! Please Contribute

  3. #3
    Join Date
    Feb 2003
    Location
    Mtl, Canada
    Posts
    2,379
    Nice diagram to explain how a 3-way switch works.

  4. #4
    Join Date
    Mar 2011
    Location
    Toledo Ohio
    Posts
    12
    I agree with Lee, you should plan on replacing the knob and tube ASAP.
    The black terminal is the common; its for the power supply or it goes to the fixture. If they're mixed up, the light will only work in one position. Using your meter and Lee's diagram you should be able to figure it out.

  5. #5
    Not to be stupid, but use the meter how?

    Put both probs on each and the one with activity is common? Put each on different ones and when there's activity than......

    Thanks, just not sure.

  6. #6
    Join Date
    Feb 2003
    Location
    McKean, PA
    Posts
    15,593
    Blog Entries
    1
    The problem is you don't know whether the power is coming into the upstairs switch or the downstairs one. My bet is that the bottom switch is getting the power. With the switches in a position so the light is on, check which wire is hot on your new switch. Then flip the switch at the top of the stairs to the bottom position and check again. That should tell you which wire is hot. Once you now which wire is hot you should be able to figure it out. You may need to check both switches this way if the power does feed the upper switch. Since the system worked before, don't move any wires on the upper switch.

    Be careful as you are working with powered switches and if you touch the metal box you could cause a spark or damage the knob & tube wires in a hidden location.
    Lee Schierer
    USNA '71
    Go Navy!

    My advice, comments and suggestions are free, but it costs money to run the site. If you found something of value here please give a little something back by becoming a contributor! Please Contribute

  7. #7
    Join Date
    Jun 2007
    Location
    Athens, GA
    Posts
    140
    Just like others have said, you want to confirm where your power is coming from first. Keep in mind that power might be feeding into the junction box for the light fixtures before going to the switch box. Here's a link with several different diagrams of 3 way alternatives that I like. Once you've isolated where the power is coming from, and cut power to the circuit, you can pull both switches and determine which of those faded wires are your travelers by joining them together at one switch box and using your continuity tester at the other. If you can still see the cable sheath on your K&T wiring in the switch box, that's another easy way to identify the travelers. The travelers attach to the brass screws on your switches. The remaining wires at the switch box should be for your common terminals, which attach to the black screw.
    Last edited by Brad Sperr; 05-24-2011 at 12:37 PM.

  8. #8
    If I rearrange the three wires on my new outlet and keep trying, and I'm going to mess anything up other than it not working? (other than damaging the wires from moving them around a lot?

  9. #9
    Quote Originally Posted by Jeremy Milam View Post
    If I rearrange the three wires on my new outlet and keep trying, and I'm going to mess anything up other than it not working?
    No, but if you couldn't figure that out yourself using the diagram Lee provided, then this project is way over your head (nothing personal, just saying....). Call an electrician before you burn your house down.

  10. #10
    I understood the diagram, just not how to use a multimeter to determine which was the common hot wire.

    Regardless, I switched two wires and it works correctly now. Both faded red that enter from the same area into the box are the travelers, the odd one is the common.

    I guess the old 3 way had the terminals in different spots than the new one.

    Thanks for all of the suggestions and advice!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •