How to Install a 3-Way Light Switch

Preparations

• 1

  Turn off the power at the circuit breaker.

• 2

  Test the wires to make sure the power is turned off with your voltage tester.

• 3

  Identify where each switch comes in the circuit by locating the wire that connects either the light or one of the switch boxes to the main power source. If the light is first, then you will need to make different connections at the middle switch box, as noted below.

3-Way Switch at the Beginning or Middle of a Circuit Before the Light

• 4

  Identify the wires coming into the switch box. You should see three wires coming in from the power source: white, black and ground (green or copper). You should have four wires that go to the light or the other switch box: white, black, red and ground (green or copper).

• 5

  Connect the two white wires together with needle-nose pliers and secure with a wire nut. For extra security, attach the nut to the wires with black tape.

• 6

  Attach a small piece of grounding wire to the grounding screw on the switch. Then, twist this wire and the other two grounding wires together with needle-nose pliers and secure with a wire nut. For extra security, attach the nut to the wires with black tape.

• 7

  Attach the black wire that comes in from the power source to the common terminal screw. This screw will be colored differently than the other screws (either black or copper).

• 8

  Attach the black wire that goes out to the other switch or to the light to one of the traveler screws.

• 9

  Attach the red wire that goes out to the other switch or to the light to one of the traveler screws.

3-Way Switch at the Middle of a Circuit After the Light

• 10

  Identify the wires coming into the switch box. You should see three wires coming in from the light: white, black and ground (green or copper wire). You should have four wires that go to the other switch box: white, black, red and ground (green or copper wire).

• 11

  Connect the two black wires together with needle-nose pliers and secure with a wire nut. For extra security, attach the nut to the wires with black tape. (Note: When the light comes before the switches in the circuit, meaning the power source connects to it before the switches, white and black wires switch places.)

• 12

  Attach a small piece of grounding wire to the grounding screw on the switch. Then, twist this wire and the other two grounding wires together with needle-nose pliers and secure with a wire nut. For extra security, attach the nut to the wires with black tape.

• 13

  Wrap black tape around the ends of the two pieces of white wire to indicate they are not "hot" wires.

• 14

  Attach the white wire that comes in from the light to the common terminal screw. This screw will be colored differently than the other screws (either black or copper).

• 15

  Attach the white wire that goes out to the other switch to one of the traveler screws.

• 16

  Attach the red wire that goes out to the other switch or to the light to one of the traveler screws.

3-Way Switch at the End of a Circuit

• 17

  Identify the wires coming into the switch box. You should see four wires coming in: white, black, red and ground (green or copper).

• 18

  Attach the ground wire to the grounding screw on the switch.

• 19

  Wrap black tape around the white wire to indicate that it is "hot."

• 20

  Attach the black wire to the common terminal screw. This screw will be colored differently than the other screws (either black or copper).

• 21

  Attach the white wire to one of the traveler screws.

• 22

  Attach the red wire that goes out to the other switch or to the light to one of the traveler screws.

Final Steps

• 23

  Place each switch into the switch box and connect it with screws.

• 24

  Place a cover plate over the switches and attach with screws.

• 25

  Turn the power back on.