When homeowners search for instructions on wiring a 2 way light switch, they are almost always trying to solve a specific problem: controlling a single light fixture from two different locations (like the top and bottom of a staircase). Here is the direct answer to get you oriented immediately:
• Line Hot (Black): Lands on the Common screw (usually black or darker brass).
• Travelers (Red & Black of 14/3): Land on the two Brass screws (interchangeable).
• Switched Load (Black to light): Lands on the second switch's Common screw.
• Neutrals (White): Bypass the switch entirely and splice together with a wire nut.
• Grounds (Bare/Green): Land on the Green grounding screw and bond to the metal box.
Terminology Note: In the UK, Australia, and parts of Europe, this two-location setup is officially called a 2-way switch. In the US and Canada (under the NEC and CEC), this exact same circuit requires a 3-way switch (which has three terminals, excluding ground). This guide uses US NEC terminology, wire colors, and code requirements, but the electrical logic applies globally.
The Terminology Trap: 2-Way vs. 3-Way
Confusion arises because a standard US single-pole switch (which controls a light from just one location) has two main terminals. Beginners often call this a "2-way" switch. However, if you buy a standard single-pole switch, you cannot wire it to a second switch. You must purchase dedicated 3-way switches (US) or 2-way switches (UK). Always look for the word "3-Way" on the US packaging, or count the terminals on the back: you need one black/dark screw (Common) and two brass/light screws (Travelers).
Decision Path: Which Switch Do You Actually Need?
Before tearing into your drywall or pulling new cable, confirm your circuit topology. Use this decision table to ensure you buy the right hardware.
| Your Goal | Switch Type Required (US) | Cable Required Between Switches | Buy This Exact Part |
|---|---|---|---|
| Control light from ONE location | Single-Pole (2 terminals) | 14/2 NM-B (or 12/2) | Leviton 5601-2W |
| Control light from TWO locations | 3-Way (3 terminals) | 14/3 NM-B (or 12/3) | Leviton 5603-2W (Qty 2) |
| Control light from THREE+ locations | Two 3-Way + One 4-Way | 14/3 NM-B between all | Leviton 5603-2W + 5604-2W |
Tools, Materials, and Device Ratings
For a standard 15-amp residential lighting branch circuit, you must match your wire gauge to your breaker. Do not mix 14 AWG wire on a 20-amp breaker.
- Switches: Two (2) Leviton Decora 15A 3-Way Switches (Model #5603-2W). Rated for 15A, 120V AC. (~$4.50 each).
- Wire: Southwire 14/2 NM-B (Power to Switch 1, Switch 2 to Light) and 14/3 NM-B (Between Switch 1 and Switch 2). Ampacity is 15A per NEC Table 310.16 (60°C column).
- Breaker: 15A Single-Pole (e.g., Square D HOM115 or Eaton BR115).
- Connectors: Ideal Wire-Nut Tan (14-12 AWG) or Purple (16-14 AWG) for splicing neutrals and grounds.
- Tools: Klein Tools 11055-6 wire strippers, Klein 32307 multi-bit screwdriver, Fluke 117 True-RMS Multimeter, and a non-contact voltage tester (NCVT).
Mains Safety and Circuit Verification
1. De-energize: Turn OFF the 15A lighting breaker at the main panel.
2. Lock/Tag: Place a piece of electrical tape over the breaker or use a physical lockout tag so no one accidentally flips it while you are working.
3. Verify Dead: Use a tested NCVT and a multimeter. Test between the black (hot) and white (neutral) wires, and black to bare ground. The meter must read 0.0V. Never trust a breaker label; always verify at the wire. Local code may require a licensed electrician for new circuit runs.
Step-by-Step Wiring: Switch 1 (Power Source Box)
This is the box where the 14/2 NM-B cable from the breaker panel enters. Under NEC Article 404.2(A) (updated in 2011), a grounded neutral conductor must be present at every switch box, even if the switch itself doesn't use it. This is for future smart-switch compatibility. Therefore, we do not use the white wire in the 14/3 cable as a traveler.
- Prepare the Wires: Strip 3/4 inch of insulation from all 14/2 and 14/3 conductors. Fold the bare ground wires back and out of the way for now.
- Splice the Neutrals: Take the White wire from the panel 14/2 and the White wire from the 14/3 going to Switch 2. Twist them together with a tan wire nut. Do not connect these to the switch.
- Bond the Grounds: Twist all bare copper grounds together with a wire nut, leaving a 6-inch pigtail to connect to the metal box (if metal) and the switch's green screw.
- Terminate the Line Hot: Connect the Black wire from the panel 14/2 to the Common screw (the single black or dark-colored screw) on Switch 1. Wrap the wire clockwise around the screw and torque to the manufacturer's spec (usually ~14 in-lbs).
- Terminate the Travelers: Connect the Black and Red wires from the 14/3 cable to the two Brass screws on Switch 1. (It does not matter which brass screw gets which color; they are interchangeable).
- Ground the Switch: Connect the bare copper pigtail to the Green grounding screw on the switch strap.
Step-by-Step Wiring: Switch 2 (Load Side Box)
This is the box where the 14/3 cable from Switch 1 arrives, and the 14/2 cable departs up to the ceiling light fixture.
- Splice the Neutrals: Take the White wire from the incoming 14/3 and the White wire from the outgoing 14/2 (to the light). Twist them together with a wire nut. Again, the switch does not touch the neutral.
- Bond the Grounds: Twist all bare grounds together, add a pigtail for the switch green screw, and bond to the box if metal.
- Terminate the Travelers: Connect the Black and Red wires from the incoming 14/3 cable to the two Brass screws on Switch 2.
- Terminate the Switched Load: Connect the Black wire from the outgoing 14/2 (going to the light) to the Common screw (black/dark screw) on Switch 2.
- Ground the Switch: Connect the bare copper pigtail to the Green grounding screw.
- At the Light Fixture: Connect the 14/2 Black to the fixture's hot (black) lead, White to neutral (white), and Bare to fixture ground.
Testing, Verification, and the Most Common Botch
Before pushing the switches back into the drywall and turning the breaker on, verify your switch logic with your multimeter.
Expected Meter Readings (Continuity Test)
With the breaker OFF and wires disconnected from the switch, set your Fluke 117 to Continuity (the soundwave icon).
- Switch 1, Toggle UP: Probe Common screw to Brass screw #1. Meter should beep (read < 1.0 ohm). Probe Common to Brass #2. Meter should read OL (Open Line / Infinite).
- Switch 1, Toggle DOWN: The continuity should swap. Common to Brass #1 reads OL; Common to Brass #2 beeps.
- If your switch behaves this way, it is functioning correctly. Re-terminate and energize.
The Most Common Botch: The Traveler/Common Swap
The Symptom: You turn the breaker on, but the light only works when Switch 1 is in the "UP" position. If Switch 1 is "DOWN", flipping Switch 2 does nothing. Alternatively, the light stays on permanently regardless of switch position.
The Cause: You accidentally landed a Traveler wire (Red or Black from the 14/3) on the Common screw (black screw), and the Line Hot or Load wire on a Brass screw. The internal mechanical wiper of the switch is now routing power to a dead-end brass terminal instead of passing it down the traveler cable.
The Fix: De-energize the circuit. Pull both switches out. Identify the single wire in Box 1 that comes from the panel (Line Hot) and the single wire in Box 2 that goes to the light (Load). Ensure only those two specific wires are on the black Common screws. The remaining two wires in each box (the Red and Black of the 14/3) must be on the brass Traveler screws.
For further reading on switch loop requirements and neutral mandates, refer to NFPA 70 (National Electrical Code) Article 404.2. For device-specific torque ratings and wiring diagrams, consult the Leviton 5603-2W specification sheet.
