3-Way Switch Diagram: Wiring a 3-Way Switch Circuit from Any Location
This is a free printable leviton 3 way switch diagram: download the diagram as SVG or open it and print to paper or PDF.
A 3-way switch circuit (called a 2-way circuit in the UK and Australia) lets you control one light fixture from two separate switch locations using a pair of single-pole double-throw switches linked by traveller wires.
A 3-way switch is a single-pole double-throw (SPDT) toggle switch with three terminals: a Common terminal (usually darker brass or black-coloured screw) and two Traveller terminals (lighter brass screws). The switch itself does not have a fixed ON or OFF position — it only toggles the common terminal between the two traveller terminals. The circuit works because both switches must route the live (hot) conductor through a continuous path to the load.
The classic US residential wiring method uses the following logic:
Line (hot) wire from the supply connects to the Common terminal of Switch 1. Two traveller wires run between the traveller terminals of Switch 1 and Switch 2. The Common terminal of Switch 2 connects to one end of the light fixture. The neutral (white) wire runs directly from the supply neutral to the other terminal of the light fixture. The safety ground (bare copper or green) bonds both switch boxes, the fixture, and the panel ground together.
When both switches direct the hot to the same traveller wire, the circuit is complete and the light is on. Flipping either switch redirects the common to the other traveller, breaking the circuit and turning the light off. Flipping either switch again restores continuity. This is why you can toggle the light from either location regardless of the other switch's position.
In the UK (BS 7671) and Australia (AS/NZS 3000), an equivalent circuit uses two-way switches wired with strappers between L1 and L2 terminals. The terminology differs — COM, L1, L2 replace Common, Traveller 1, Traveller 2 — but the electrical principle is identical.
For three-location switching, an intermediate switch (4-way in US terminology, intermediate switch in UK terminology) is inserted in the traveller loop between the two 3-way switches. Each additional location requires one additional intermediate switch.
NOTE: This diagram is generic and illustrative. Always consult a licensed electrician and follow the applicable wiring code for your jurisdiction (NEC/NFPA 70, BS 7671, AS/NZS 3000, IEC 60364) before undertaking any mains wiring work.
How to wire leviton 3 way switch diagram
- Isolate the circuit and verify dead Switch off the circuit breaker supplying the lighting circuit. Use a non-contact voltage tester or multimeter at all terminals in both switch boxes and the light fixture box to confirm zero voltage. Apply a lock-out/tag-out to the breaker before touching any conductors.
- Identify cable conductors at each switch box In the supply-end switch box, identify the incoming cable (hot/live, neutral, ground) and the cable running to Switch 2 (traveller cable). In the load-end switch box, identify the traveller cable from Switch 1 and the cable running to the light fixture. Label each conductor before disconnecting any existing wiring.
- Wire Switch 1 (supply end) Connect the hot (black) wire from the supply cable to the Common terminal (dark screw) of Switch 1. Connect the two traveller wires (e.g. black and re-identified white) to the two Traveller terminals (lighter screws) of Switch 1. Connect the ground wire to the switch's ground screw and to the metal box ground (if metal box).
- Wire Switch 2 (load end) Connect the traveller wires (matching the connections at Switch 1) to the two Traveller terminals of Switch 2. Connect the switched hot wire running to the fixture to the Common terminal of Switch 2. Connect the ground wire to Switch 2's ground screw. The neutral wire passes through this box and continues directly to the fixture without connecting to the switch.
- Wire the light fixture Connect the switched hot wire from the Common of Switch 2 to the black (live) terminal of the fixture. Connect the neutral wire from the supply to the white (neutral) terminal of the fixture. Connect the ground to the fixture's ground screw or the metal fixture box.
- Restore power and test from both locations Replace all switch covers and the fixture. Restore power at the breaker. Test the light from Switch 1 — it should toggle the light on and off. Then test from Switch 2 — it should also toggle the light on and off regardless of Switch 1's position. If only one switch controls the light, the traveller wires or Common connections are incorrect.
- Re-identify any white wires used as hot conductors Any white wire used to carry a switched hot or traveller conductor (not neutral) must be re-identified with black or red tape at both exposed ends, at both switch boxes, and at the fixture box. This is a code requirement (NEC Article 200.7, BS 7671, etc.) and a safety practice for future maintenance workers.
Specifications
| Switch type | Single-pole double-throw (SPDT), 3-terminal |
|---|---|
| Terminals | 1 × Common (dark screw), 2 × Traveller (light screws) |
| Typical rating (US residential) | 15 A, 120/277 V AC |
| Typical rating (UK/EU) | 10 A, 240 V AC |
| US cable for 15 A circuit | 14 AWG NM-B (14/2 and 14/3 with ground) |
| UK cable for standard lighting circuit | 1.5 mm² twin and earth (CPC included) |
| Third location switching | Requires one intermediate (4-way) switch per additional location |
| Applicable codes | NEC/NFPA 70 (US), BS 7671 (UK), AS/NZS 3000 (AU/NZ), IEC 60364 |
Safety warnings
- Mains electrical work is dangerous and potentially fatal. Always isolate the circuit at the breaker and verify absence of voltage with a calibrated tester before touching any conductors. Lock out and tag out the breaker. Follow NEC/NFPA 70 (USA), BS 7671 (UK), AS/NZS 3000 (Australia/NZ), or the applicable local electrical code. In many jurisdictions, mains wiring work must be performed or inspected by a licensed electrician.
- Never assume a circuit is de-energised based on a switch position alone. A 3-way switch circuit may have conductors energised in the switch box even when the light is off. Always test with a voltage tester at the terminals before working.
- Use cables rated for the circuit amperage. Under-rated cables overheat and create a fire risk. In the US, use 14 AWG for 15 A circuits and 12 AWG for 20 A circuits. Do not mix wire gauges on the same circuit.
- All ground conductors must be connected and continuous throughout the circuit — to both switches, the fixture, and the panel. An incomplete ground is a shock and fire hazard.
- Re-identify any white conductor used as a hot or traveller (not neutral) with black or red tape at all exposed ends. Failure to do so creates a hidden shock hazard for future workers who assume white = neutral.
Tools needed
- Non-contact voltage tester
- Digital multimeter (continuity and voltage)
- Flathead and Pozidrive screwdrivers
- Wire strippers
- Long-nose pliers
- Electrical tape (black and red for re-identification)
- Wire nuts or approved connectors
- Lockout/tagout kit
Common mistakes
- Connecting the hot supply wire to a Traveller terminal instead of the Common terminal on Switch 1. This results in the light being permanently on in one switch position and the circuit not responding correctly to Switch 2.
- Mixing up the Common and Traveller terminals at Switch 2, causing one switch position to work correctly and the other to either short circuit the travellers or leave the light permanently off.
- Failing to re-identify white conductors used as travellers or switched hots, leaving an unlabelled shock hazard for future electricians.
- Running neutral through a switch box and connecting it to the switch terminal, confusing it with the switched hot. The neutral should pass through the box without connecting to the switch in a standard 3-way circuit.
- Using a single-pole switch for one of the 3-way positions, resulting in a circuit that only works from one location.
- Not connecting grounds to switch screws and metal boxes, leaving the metalwork un-bonded and creating a shock hazard if a live wire contacts the box.
Troubleshooting
- Light works from Switch 1 only — Switch 2 does nothing
- Cause: The traveller wires are connected to the wrong terminals at Switch 2 (both to travellers instead of one to Common), or the Common and a Traveller terminal are swapped at Switch 2 Fix: De-energise the circuit. At Switch 2, identify the Common terminal (dark screw). Ensure the wire to the fixture connects to the Common, and the two traveller wires connect to the two Traveller terminals. Test again.
- Light is permanently on regardless of switch positions
- Cause: Both traveller wires are connected together at a splice, bypassing the switches, or the hot supply is connected directly to the fixture Fix: De-energise the circuit and trace the hot conductor from the supply panel through Switch 1, the travellers, Switch 2, and to the fixture. Verify no unintended direct connection exists between supply hot and the load wire.
- Light flickers when switches are operated
- Cause: Loose terminal screw connections at switch Common or traveller terminals, or a loose splice in the switch or fixture box Fix: De-energise the circuit. Inspect and retighten all terminal screws. Check all wire nut splices for loose connections by pulling gently on each conductor. Re-make any loose splices with fresh wire nuts.
- Breaker trips when light is switched on
- Cause: Short circuit in the fixture wiring or a traveller wire grounding out against the metal box Fix: De-energise the circuit. Inspect wiring in the switch boxes and fixture box for conductors with damaged insulation touching bare metal. Repair or replace damaged cable sections. Check that wire nut splices are fully insulated and not touching the box.
- Neither switch controls the light — light stays off
- Cause: Hot supply wire connected to a Traveller terminal at Switch 1 instead of the Common; or Common at Switch 2 not connected to the fixture Fix: De-energise the circuit. Verify the hot supply wire connects to the dark (Common) screw at Switch 1. Verify the wire to the fixture connects to the dark (Common) screw at Switch 2. Test continuity of the traveller wires end to end.
Frequently asked questions
What is the difference between a 3-way switch (US) and a 2-way switch (UK)?
They are electrically identical SPDT switches used in two-location lighting control circuits, just named differently by country. The US calls them '3-way' because they have 3 terminals. The UK and Australia call the circuit '2-way' because it controls a light from 2 locations. The wiring principle and switch construction are the same.
How do I identify the Common terminal on a 3-way switch?
The Common terminal is usually the darkest screw on the switch — typically a black or dark bronze colour — while the two traveller terminals are lighter brass. Some switches stamp 'COM' or 'COMMON' on the housing. Always verify with the switch manufacturer's documentation or a continuity test before wiring.
Why does one of my traveller wires need to be re-identified with coloured tape?
In older wiring, a 2-conductor cable (black + white + ground) is used as the traveller cable. The white wire in this cable carries the switched hot (not neutral), so electrical codes require it to be re-identified by wrapping it with black or red electrical tape at both ends to indicate it is a hot conductor, not a neutral.
Can I use a regular single-pole switch as a 3-way switch?
No. A single-pole switch has only two terminals and switches the circuit open or closed. A 3-way switch has three terminals and routes the common to one of two travellers. Using a single-pole switch in a 3-way circuit will result in the light being controllable from only one location, or a permanent short/open circuit.
How do I add a third switching location to a 3-way switch circuit?
Insert an intermediate switch (called a 4-way switch in US terminology) in the traveller loop between the two existing 3-way switches. An intermediate switch has four terminals and crosses or straight-connects the two traveller pairs based on its position. One intermediate switch is needed per additional control location.
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