Control one light from two places. Choose your setup, then flip either switch on the diagram: the glowing wires show how power travels through the two travelers.
Guide
How 3-way switches work
Each 3-way switch has a dark COMMON screw, two brass traveler screws and a green ground. Inside, the common connects to one traveler or the other. One switch’s common gets the incoming hot, the other switch’s common feeds the light, and the two travelers run between the switches, usually the red and black wires of a 14/3 cable.
The mistake almost everyone makes
When replacing a 3-way switch, mark the wire on the dark COMMON screw before removing the old switch. If the common wire ends up on a traveler screw, the light works only in some switch positions. The two traveler wires can go on either brass screw.
Cable you need
Between the two switches you need 14/3 cable (12/3 on a 20 A circuit): black and red as travelers, white as neutral, bare as ground. Most codes now require a neutral in switch boxes, which also lets you add a smart switch later.
As an Amazon Associate we earn from qualifying purchases, at no extra cost to you.
Frequently asked questions
Which screw is common on a 3-way switch?
The dark (black or bronze) screw, often marked COM. The two lighter brass screws are travelers.
Does it matter which traveler goes on which brass screw?
No. The two travelers are interchangeable on either switch, as long as the common wire is on the common screw.
Why does my 3-way switch only work when the other switch is in one position?
The common wire and a traveler are swapped on one of the switches. Find the wire that is hot in both positions of the other switch (with care, or ask an electrician) and move it to the COMMON screw.
Can I put a smart switch in a 3-way circuit?
Yes, with a smart 3-way kit: a main smart switch plus a companion or wireless remote from the same brand. Most main switches need a neutral, so check with our neutral wire checker.
Can I add a third switch location?
Yes. Add a 4-way switch between the two 3-way switches. See the 4-way switch wiring diagram.
