4-Way Switch Wiring - Power Source 1st switch, Fixture Feed 3rd switch

At the ceiling box - the ungrounded conductor {aka hot} from the fixture (could be a brass colored screw) connects to the black wire from the switch 3. The white wire from switch 3 is the grounded leg conductor {aka neutral} for the fixture (could be a silver color screw).

Bare wires are together and grounded to box (if metallic) and if the fixture has a green wire or a grounding screw, it gets grounded also. Bares and green wires are equipment grounding conductors.

Be sure to read any documentation that comes with your fixture

If you need onward power from the fixture

If only switched power required onward then at existing fixture...

• onward cable - black/white/bare
• connect black from onward cable to the black from switch 3.
• connect white from onward cable to white wire from switch 3.
• connect bare from onward cable to other bares and to electrical box if metallic.
• At the onward cables destination, the black is the switched ungrounded conductor {aka hot}, the white is the grounded leg {aka neutral}, and the bare is the equipment grounding conductor.

If only unswitched power required onward then at existing fixture...
Onward unswitched power is not possible with this configuration as not unswitched ungrounded conductor {aka hot} exists at thef ixture location.

If you need onward power from the switch

NOTE: Onward power...Only unswitched power is available at switch box 1. Only switched power is available at switch box 3. Onward power is not possible from switch box 2 as no unswitched or switched ungrounded conductor {aka hot} exists at switchbox 2.

• onward cable - black/white/bare
• connect black from onward cable to the black from switch 3 (black from switch 3 going to fixture)
• connect white from onward cable to white wire from switch 2.
• connect bare from onward cable to other bares and to electrical box if metallic.
• At the onward cables destination, the black is the switched ungrounded conductor {aka hot}, the white is the grounded leg {aka neutral}, and the bare is the equipment grounding conductor.

If only unswitched power required onward then at existing switch 1...

• onward cable - black/white/bare
• connect black from onward cable to the black from circuit power supply cable
• connect white from onward cable to white wire from circuit power supply cable.
• connect bare from onward cable to other bares and to electrical box if metallic.
• At the onward cables destination, the black is the ungrounded conductor {aka hot}, the white is the grounded leg {aka neutral}, and the bare is the equipment grounding conductor.

The common screw on a 3 way switch is the odd color screw

If wiring multiple fixtures be sure to check the following guidelines concerning how to do it and what not to do: Wiring Multiple Fixtures.

If you are new at understanding the "politically correct" electrical terminology and need clarification of the terms used, we strongly urge you to read the Clarification of Definitions and Terminology guide. This will explain the terminology used in this article.

Also, be sure to read "Identifying the Correct Screws on 4-Way and 3-Way Switches".