2-Way Light Switch Wiring Diagram
This is a free printable 2 way light switch wiring: download the diagram as SVG or open it and print to paper or PDF.
Two-way light switch wiring lets you control one light from two separate switch locations — both ends of a staircase, for example — using two 2-way switches connected by two traveller conductors, with each switch having a common terminal and two traveller terminals.
A 2-way switching circuit is one of the most common wiring configurations in residential and commercial buildings. The purpose is straightforward: you should be able to turn a light on or off from either of two locations regardless of the switch's current position. Flipping either switch always changes the state of the light.
Terminology note: In the UK and many Commonwealth countries (including South Africa and Australia), these are called '2-way switches.' In the USA and Canada, the equivalent device is called a '3-way switch' (because it has three terminals). The number refers to how many connections the switch has, not how many positions. A UK 2-way switch has three terminals; a US 3-way switch also has three terminals. They are functionally identical — only the naming convention differs.
How the circuit works: Each 2-way switch has one common (COM) terminal and two traveller terminals (L1 and L2 in UK convention; or sometimes marked with colours). Two conductors — the travellers — run between the two switches, connecting the L1 terminal of one switch to the L1 terminal of the other, and L2 to L2. The COM terminal on the first switch is connected to the live supply; the COM terminal on the second switch feeds the load (light fitting).
When both switches are in the same relative position, the circuit is complete and the light is on. Moving either switch to its other position breaks the circuit and turns the light off — and moving either switch again reconnects it.
Power can be routed via the switch or via the light (loop-at-light method). Modern wiring regulations in many jurisdictions require the switch feed to be identified with a specific colour at the switch to indicate it is a switched live conductor. Always refer to the wiring regulation in your jurisdiction: BS 7671 (UK), SANS 10142 (South Africa), AS/NZS 3000 (Australia/New Zealand), or NEC/NFPA 70 (USA).
Two-way light switch wiring becomes more versatile when extended to 3-way configurations. When power feeds the light fixture instead of the switch box, the hot wire arrives at the light and must be looped back to the switch via cable, which calls for a 3-wire cable run. For ceiling fan and light combos, a 3-way setup using a 4-wire cable between switch and fan canopy gives independent fan-speed and light control. UK 3-way installations use 2-way switches on each end with intermediate switches in between, wired to L1, L2, and COM per BS 7671. Sketch your specific scenario in the free browser-based editor to catch any cable routing conflicts before you start work.
How to wire 2 way light switch wiring
- Switch off the circuit at the consumer unit and verify Turn off the correct fuse or MCB at the consumer unit (fuse board) and use a non-contact voltage tester to confirm that all conductors at the switch positions and light fitting are dead before touching any wiring.
- Identify the cable requirements for your layout Between the consumer unit and the first switch: one 2-core + earth cable (carries supply live and neutral). Between the two switch boxes: one 3-core + earth cable (carries the two travellers and a switched live). Between the second switch and the light fitting: one 2-core + earth cable (switched live and neutral).
- Wire the first 2-way switch Connect the incoming supply live conductor to the COM terminal of the first switch. Connect the two remaining cores of the 3-core cable (travellers) to the L1 and L2 terminals. The neutral and earth conductors are not interrupted at switches — run them through to the light fitting.
- Wire the second 2-way switch Connect the two traveller conductors from the first switch to the L1 and L2 terminals of the second switch — L1 to L1, L2 to L2. Connect the switched live output (going to the light) to the COM terminal of the second switch.
- Identify switched conductors Any conductor that carries live potential when the switch is on — but is not the permanent live — must be marked as a live conductor per your local wiring regulations. In the UK (BS 7671), reidentify with brown sleeving or tape at each termination point. In South Africa (SANS 10142), follow the current edition's core colour requirements.
- Connect the light fitting Connect the switched live (from COM of the second switch) and the neutral to the light fitting terminals. Connect the earth conductor to the fitting earth terminal (if metal) or the circuit earth at the backplate. Ensure all terminals are tight and no bare conductors are exposed outside terminals.
- Test the circuit before closing switch covers Restore power at the consumer unit. Test each switch independently — operating either switch should toggle the light on or off regardless of the other switch's position. If the light only works in one combination, recheck common terminal connections at both switches.
Specifications
| UK/Commonwealth terminology | 2-way switch (3 terminals: COM, L1, L2) |
|---|---|
| US/Canada equivalent terminology | 3-way switch (3 terminals: Common, Traveler 1, Traveler 2) |
| Supply voltage (UK/SA/AU) | 230 V AC, 50 Hz |
| Supply voltage (USA) | 120 V AC, 60 Hz (residential) |
| Typical switch rating (residential) | 6 A or 10 A at 230/250 V AC |
| Minimum cable size (UK/SA lighting circuit) | 1.5 mm² copper for circuits up to 16 A MCB |
| Cable between switch positions | 3-core + earth (two travellers plus additional conductor) |
| Applicable standards | BS 7671 (UK), SANS 10142-1 (SA), AS/NZS 3000 (AU/NZ), NEC NFPA 70 (USA) |
Safety warnings
- Always switch off the correct MCB or fuse at the consumer unit before touching any wiring, and verify the circuit is dead at the switch and light positions using a calibrated voltage tester. Do not rely on the switch being in the off position — a 2-way circuit always has a live conductor at the switch even when the light is off.
- Fixed electrical wiring work must be carried out by a competent person and, where required, inspected and tested in accordance with local regulations: BS 7671 (UK), SANS 10142-1 (South Africa), AS/NZS 3000 (Australia/NZ), or NEC/NFPA 70 (USA). Many jurisdictions require notification to the local authority or a certificate of compliance.
- Re-identification of conductor colours is mandatory where conductors carry different functions than their sheathing colour implies. A grey or black conductor used as a switched live must be marked brown at every termination point per BS 7671; follow equivalent local requirements in other jurisdictions.
- Earth conductors must be continuous throughout the circuit and connected at every metalwork point (metal switch plates, metal conduit, metal light fittings). Never omit the earth connection.
- Do not exceed the switch or cable current rating. A standard lighting switch rated 6 A should not be used with loads exceeding 6 A (approximately 1 380 W at 230 V). High-wattage LED drivers or transformers with high inrush current may require a switch with a higher inrush rating.
Tools needed
- Non-contact voltage tester
- Digital multimeter
- Insulated screwdrivers (flathead and Phillips)
- Wire strippers
- Side cutters
- Conductor core identification sleeving or tape (brown, blue, green/yellow per BS 7671 or local equivalent)
- Cable clips and installation tools for surface or concealed wiring
Common mistakes
- Connecting the supply live to an L1 or L2 traveller terminal instead of the COM terminal — the light will work in only one switch combination and the other will appear dead.
- Crossing the traveller connections — connecting L1 of one switch to L2 of the other — which makes the circuit operate inverted but does not prevent it working; however it can cause confusion when adding an intermediate 4-way switch later.
- Using 2-core cable between the switch positions instead of 3-core — you need two travellers and, depending on the layout, a switched live or neutral in this run.
- Failing to mark re-identified conductors — a grey conductor used as a live must be sleeved or taped at every termination to avoid future confusion and comply with regulations.
- Omitting earth conductors at metal switch plates or metal light fittings — all exposed metalwork must be earthed.
- Not testing both switches independently before closing covers — a common terminal fault may allow the circuit to work in one switch position combination but fail in the other.
Troubleshooting
- Light only works in one combination of switch positions
- Cause: Common terminal miswired — supply or load connected to L1 or L2 instead of COM on one or both switches Fix: Switch off at consumer unit, verify dead. Remove switch cover at each location and check that the incoming supply live connects to COM on the first switch, and the switched live going to the light connects to COM on the second switch. L1 and L2 carry only the travellers.
- Light stays on permanently regardless of switch position
- Cause: Traveller conductors shorted together at a terminal, or switch mechanism faulty (internally shorted) Fix: Isolate the circuit. Disconnect the traveller conductors from one switch and check for continuity between them at the other switch — there should be none with both conductors free. If there is continuity, the switch body is shorted internally. Replace the faulty switch.
- No light in any switch position
- Cause: Open circuit — broken neutral, broken earth creating an open (if RCD-protected), blown fuse, or tripped MCB Fix: Check the consumer unit for a tripped breaker first. Then check continuity of the neutral conductor from the consumer unit to the light fitting. Check the light bulb. Verify the COM terminal connections and that traveller continuity exists through both switches.
- RCD trips when light is switched on
- Cause: Earth fault — conductor damaged and contacting metalwork, or damp in a light fitting or junction Fix: Isolate the circuit. Inspect the light fitting for moisture ingress and the wiring at all termination points for damaged insulation. Use a megohmmeter (insulation resistance tester) to test insulation resistance on the circuit conductors.
Frequently asked questions
Why is a 2-way switch called a 3-way switch in the USA?
The naming convention is different. In the US, switches are named by the number of terminals — a 3-way switch has three terminals (one common and two travellers). In the UK and Commonwealth countries, they are named by the number of positions or circuit connections, giving the same device a different name. They are functionally identical.
Can I use a standard single-way switch as a 2-way switch?
No. A standard one-way (single-pole) switch has only two terminals and simply opens or closes one conductor. A 2-way switch has three terminals and internally routes its common terminal to one of two possible outputs. You cannot create a 2-way circuit with single-pole switches.
What are the traveller conductors?
The travellers are the two conductors that run between the L1 and L2 terminals of the two 2-way switches. They carry the live potential alternately depending on switch position. In a three-core cable (plus earth), the two insulated conductors other than the switched live are used as travellers.
Why does my 2-way switch circuit work at one switch but not the other?
The most likely cause is that the traveller conductors are incorrectly connected — one of the L1 or L2 terminals on a switch has a traveller where the common should be, or vice versa. Remove the switch covers, identify the common terminal (usually marked COM or a different colour), and verify the supply feeds COM on switch 1 and the load feeds COM on switch 2.
Can I add a third switch location to a 2-way circuit?
Yes, but you need to add a 4-way switch (called an intermediate switch in UK terminology) between the two 2-way (3-way) switches. The 4-way switch intercepts the two traveller conductors and can cross-connect or pass them through — either position will toggle the light state. There is no limit to how many 4-way switches you can add.
How do you wire a 3-way switch when power is at the light fixture?
When the supply enters at the light box, run a 3-wire cable (black, red, white + ground) from the light to the first 3-way switch. Connect the black wire to the COM terminal of that switch, and use the red and white (re-identified with black tape) as travellers to the second switch. At the second switch connect the hot travellers to the two traveller terminals and the switched hot from COM back to the light fixture black load wire. Both neutrals join at the light box.
How do you wire a 3-way switch to control a ceiling fan and a light separately?
Run a 4-wire cable (black, red, white, ground) between the double-switch gang box and the fan canopy. Use black as the fan-speed switched hot and red as the light-kit switched hot, with white as neutral and bare or green as ground. Each 3-way switch pair — one for fan, one for light — controls its respective circuit independently. The fan's motor and light-kit leads connect to black and red respectively inside the canopy, and both neutrals join to white.
How do you wire a 3-way switch when the light fixture is in the middle of the run?
With the light in the middle, a 3-wire cable runs from the first switch to the light box and a second 3-wire cable continues from the light box to the second switch. At the light box, splice the traveller wires straight through without interruption — they must reach both switches unbroken. The switched hot (COM output) from the second switch feeds the light fixture, and the neutral is spliced through at the light box to complete the circuit. Label all re-identified conductors clearly.
How do you wire a 3-way switch when power and light are in the same box?
When supply and fixture share one box, run a 3-wire cable from that box to the first 3-way switch and another 3-wire cable between the two switch boxes. At the fixture box connect the supply hot to the COM of the first switch via the cable, use the remaining two conductors as travellers to the second switch, and return the switched hot from the second switch's COM back to the fixture's black load wire. Neutrals splice at the fixture box only.
How do you wire a 3-way light switch in the UK?
UK 3-way switching uses a pair of 2-way switches (with COM, L1, and L2 terminals) and one intermediate switch for each additional location. Live (brown) connects to COM of the first switch; the strapping conductors (any spare cores, sleeved appropriately) link L1-to-L1 and L2-to-L2 between switches; switched live (brown-sleeved grey) leaves the final switch's COM and feeds the lamp. Neutral (blue) runs directly to the lamp. The circuit must comply with BS 7671 18th Edition wiring regulations.
Related diagrams
- 1 gang 2 way switch wiring diagram
- 1 way light switch wiring diagram
- 2 gang 1 way switch wiring diagram
- 2 gang 2 way switch wiring diagram
- 2 humbuckers 1 volume 1 tone 3 way switch diagram
- 2 way dimmer switch wiring diagram