wiring a three-way switch

One of the things I discovered when I moved into my home is that the three-way switches were installed incorrectly.  Three-way switches are designed to allow you to control a light from two different switches.  

You should be able to turn the light on or off from either switch, regardless of the position of the other switch.  If the switches are wired incorrectly, they won't operate independently of each other.  When that happens, you have to rewire them.


If you are at all mechanically inclined, you can do the rewiring yourself without having to hire an electrician.


  1. Turn off the power to the light fixture at the circuit breaker.
  2. Take the covers off both switches, and carefully pull out the switches, leaving them connected to the wires.
  3. Using a voltmeter, test the switches to verify that the power is off.
  4. Remove the wires from the switches.  One switch box will have just one set of wires coming into the box (this is the "remote" switch).  The other box will have three sets of wires coming into the box (this is the "master" switch - if there are more than three sets of wires coming into the box, you should probably call an electrician).
  5. On the remote switch, plug the black wire into the single black screw of the switch, and the red and white wires into the top silver or brass screws (it doesn't matter which wire goes to which screw).
  6. On the master switch, find which wires are coming from the remote switch, which wires go to the light fixture, and which supply the juice from the circuit breaker panel (this may require some careful testing with the circuit breaker on).
  7. Take one wire from the light fixture and connect it to the black wire coming from the remote switch (always use screw caps when connecting wires).
  8. Take the other wire from the light fixture and connect it to one of the "hot" power wires (with the circuit breaker off).
  9. Take the remaining power wire and connect it to the bottom (black) screw on the master switch.
  10. Take the red and white wires coming from the remote switch and connect it to the two top silver or brass screws on the master switch.
Put everything back into the switch boxes, test it out, and it should work!  If it doesn't, turn off the circuit breaker, and call an electrician.

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