7 posts / 0 new
Last post
William
3 Way Connections

I'm installing new electrical boxes and wiring to a 3 way light switch. I had marked where the wires go but somehow while running the wires into the box the labels fell off. What is the best way to trace these wires down with a meter so I know where to hook them up on the new 3 way switch? One wire should be hot, and the other two should toggle right? Or does the hot wire toggle depending on where the other switch is set? :confused:

Fencepost
Re: 3 Way Connections

If the other 3-way switch is intact, note the wire that's hooked to the dark-colored screw. The OTHER TWO wires (connected to the light-colored screws) will be the opposite end of the two wires in this switch box that must also connect to the light-colored screws (doesn't matter which is which). The remaining wire, to be connected to the dark screw, will be either hot, or it will go to the hot side of the light fixture.

Armed with that information, you may be able to do some continuity testing to determine which are the "other two wires." (These are commonly called "travelers.")

JLMCDANIEL
Re: 3 Way Connections

To answer your question, it will depend on which switch you are dealing with. If it is the one connected to power then one wire will always be hot and the other two will be travelers, if it is the switch connected to the light then the travelers carry power to the switch and the other wire is switched on and off. Standard wireing would be with 3 conductor cable with the white and red being travlers and the black being hot or the switched lead to the light.

Jack

dcalabro
Re: 3 Way Connections

Hopefully you have the privilege of having newer colored wire that is white/black or white/black/red. The link below has a few 3way diagrams to help visualize what you have. See if you can figure out which matches closest to what you have. Only advice I can give is stop and think and double check.

http://www.electrical-******.com/electrical/diagrams/

When the power is back on and you're testing your end result, make sure both switches work when the other is toggled. In one situation I wired it incorrectly so once I turn off lights using the upstairs switch, the downstairs switch wouldn't work anymore and I had to go upstairs to turn them back on.

William
Re: 3 Way Connections

OK thanks for the link, I'll study that in a bit. First I had a question about testing the wires with a meter. The downstairs switch is the one that I need to wire. The upstairs switch hasn't been touched except for the cover being taken off. The screws are a bit discolored so I don't want to rely on going by the coloring. I'll put one side of my meter on what appears to be the different colored screw on the upstairs switch. When I go downstairs two of the wires show continuity and the meter beeps.

Does that sound right or is there a short?

PS - link doesn't work.

JLMCDANIEL
Re: 3 Way Connections

Try flipping the switch upstairs, one of the travelers and the common would be shorted through the switch. This is normal. By the way on the link above replace the ****** with o n l i n e for some reason the sites spam filter replaces the word with *'s. If you are using a meter try different combinations until you find continuity on one line, that is a traveler then flip the switch and try again until you only have one wire with continuity, that is the second traveler. The remaining wires go on the common.

Jack

William
Re: 3 Way Connections

Yep that was it. I studied the diagram for how they should be wired and it makes complete sense now. The travelers connect the two switches together, and the common connector goes to the lights white and main hot wire. Really cool! :)

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.