4-Way Light Switch Wiring Diagram

4-Way Light Switch Wiring Diagram — interactive diagram. Open it in the editor to customise components and wiring.

This is a free printable 4 way light switch diagram: download the diagram as SVG or open it and print to paper or PDF.

Clear reference for 4-way (intermediate) light switch circuits showing how to control a single light from three or more switch locations using 3-way and intermediate switches.

A 4-way switch installation controls one or more light fixtures from three or more locations. The term '4-way' refers to the intermediate switch at the centre of the circuit, which has four terminals. In UK and international terminology, this intermediate switch sits between two 3-way switches (called two-way switches in the UK). In North American terminology, the end switches are called 3-way and the middle switches are called 4-way.

The circuit topology is straightforward: the line (live) conductor enters the first 3-way switch. From there, two traveller conductors run to the first terminal pair of the 4-way (intermediate) switch. The 4-way switch's second terminal pair connects via another two traveller conductors to the second 3-way switch. The neutral conductor runs directly to the light fixture, and a switched live returns from the last 3-way switch to the fixture.

The 4-way switch performs a single mechanical function: it connects its two input travellers to its two output travellers in either straight-through configuration (IN1 to OUT1, IN2 to OUT2) or crossed configuration (IN1 to OUT2, IN2 to OUT1). Toggling the switch alternates between these two wiring states. This means every combination of toggle positions across all switches produces a predictable circuit state, and flipping any single switch always changes the fixture state (on to off, or off to on).

Multiple 4-way switches can be chained in series between the two terminal 3-way switches. Each additional 4-way switch allows an additional control location. The traveller cables between each pair of switches carry the same two conductors throughout.

Wiring standards vary by jurisdiction. In the UK, wiring must comply with BS 7671 (18th Edition, Amendment 2 or current). In North America, compliance with NEC (NFPA 70, current edition) is required. In Australia and New Zealand, AS/NZS 3000 applies. Always work to the current edition of the applicable standard. Mains voltage wiring must only be carried out by a licensed electrician in most jurisdictions.

A 4-way switch is inserted between two 3-way switches to allow control of one light from three or more locations — common in long hallways, staircases, and large rooms with multiple entry points. The 4-way switch itself has four terminals (two pairs of travellers) and toggles which pair is connected through, reversing the traveller path. For a single-light circuit controlled from three locations you need exactly two 3-way switches at the ends and one 4-way switch in the middle. You can draw this multi-switch arrangement clearly in the free browser editor at circuitdiagrammaker.com.

How to wire 4 way light switch diagram

Plan the switch locations and cable routes Identify all switch locations and the fixture position. Sketch the circuit showing the line entry point, each switch location in sequence, and the fixture. Count the number of switch positions to determine how many 3-way end switches and how many 4-way intermediate switches are needed. Each inter-switch segment requires a 3-core cable (one earth, one traveller, one traveller) in addition to the line and switched-line conductors at the end points.
Select compliant cable and switch hardware Choose cable type and rating appropriate to the load and installation method, compliant with the applicable wiring standard (BS 7671, NEC, AS/NZS 3000, or IEC 60364). For UK installations, twin and earth cable (with an additional core for the traveller segments, or a 3-core and earth cable) must be used between intermediate positions. For North American work, 14/3 or 12/3 NM cable (or equivalent in conduit) is required between switches.
Wire the first 3-way (two-way) end switch Connect the line conductor to the common (COM) terminal of the first end switch. Connect two traveller conductors to the two remaining terminals (L1 and L2, or traveller terminals). These two travellers run to the first 4-way switch. Identify and sleeve or label any repurposed conductors as required by your applicable wiring standard.
Wire the 4-way (intermediate) switch The two travellers arriving from the previous switch connect to one pair of terminals on the 4-way switch (typically labelled IN or L1/L2 on one side of the switch). The two outgoing travellers to the next switch connect to the second pair (typically OUT or L3/L4). Do not mix IN and OUT conductors within a pair, as this inverts the switching logic for some combinations.
Wire the second 3-way (two-way) end switch The two traveller conductors arriving from the last 4-way (or from the first end switch if only three locations) connect to the L1/L2 traveller terminals of the second end switch. The common terminal of this switch connects to the switched-live conductor, which runs to the light fixture.
Connect the light fixture At the fixture, connect the switched-live from the last 3-way switch common terminal to the live terminal of the fixture. Connect the neutral conductor (which has run directly from the supply, not through any switch) to the neutral terminal. Connect the circuit protective conductor (earth) to the fixture earthing terminal.
Test all switch combinations before closing up With the circuit powered, test every combination of switch positions. Count the total combinations: two positions per switch, so three switches give eight combinations, four switches give sixteen. In every case, toggling any one switch must change the fixture state. If any combination fails this test, the circuit has a wiring error. Isolate and investigate before closing switch boxes or junction points.

Specifications

Applicable wiring standard (UK)	BS 7671: Requirements for Electrical Installations (18th Edition, current amendment)
Applicable wiring standard (North America)	NEC / NFPA 70, current edition
Applicable wiring standard (Australia/NZ)	AS/NZS 3000: Wiring Rules, current edition
Typical switch current rating (UK domestic)	6 A or 10 A (select to suit load)
Number of end (3-way/two-way) switches per circuit	Always exactly 2
Number of intermediate (4-way) switches	Total locations minus 2
Cable type between switches (UK)	3-core and earth, 1.0 mm² or 1.5 mm²

Safety warnings

Mains voltage wiring is potentially lethal. All work on mains circuits must be carried out by a licensed or registered electrician in compliance with the applicable wiring standard: BS 7671 (UK), NEC/NFPA 70 (USA and Canada), AS/NZS 3000 (Australia/New Zealand), or IEC 60364 (international). This diagram is a reference only and not a substitute for formal training, qualifications, and required permits.
Always isolate the circuit at the consumer unit (distribution board) by switching off the appropriate MCB and locking it off before touching any wiring. Use a non-contact voltage tester or multimeter to verify the circuit is dead before handling any conductors. Never assume a circuit is isolated because a switch is in the off position.
In the UK, any new or replacement switch circuit in a dwelling is notifiable work under Part P of the Building Regulations unless carried out by a registered competent person. Unregistered work must be notified to the local authority building control department and inspected.
Identify and sleeve any conductors that are repurposed as live conductors (for example, using the red or blue core of a twin-and-earth as a traveller). UK wiring regulations require brown sleeving on any conductor used as live. Leaving unmarked conductors is a safety risk for future maintenance workers.

Tools needed

Non-contact voltage tester (verify isolation before touching any conductor)
Flathead and Pozidrive screwdrivers (terminal screws)
Wire stripper appropriate to cable gauge in use
Continuity tester or multimeter (for testing traveller conductor routing)
Cable fishing tools (rods, draw cord) if installing in existing walls
Circuit lock-off device or warning tag for consumer unit MCB

Common mistakes

Using a standard two-way switch instead of a true intermediate switch in the middle position of the circuit. A two-way switch does not have the correct internal switching matrix; the result is a circuit that works in some combinations but not others.
Connecting the traveller conductors to the COM and one traveller terminal of the intermediate switch instead of using both dedicated traveller pairs. This happens when the installer mistakes an intermediate switch for a two-way switch.
Omitting the earth conductor at each switch position. Metallic switch faceplates, back boxes, and conduit must be earthed. Even plastic faceplates require the earth to be connected in the back box for safety.
Running the neutral conductor through a switch rather than directly to the fixture. Switching the neutral (while leaving the live permanently connected to the fixture) means the fixture remains live even when the switch is off. This is dangerous for maintenance and illegal under most wiring standards.
Not testing all switch combination states before plastering over or closing switch boxes. A wiring error discovered after closure requires destructive investigation to find and fix.

Troubleshooting

Light works from some switch positions but not others: Cause: Incorrect terminal assignment on the 4-way (intermediate) switch — one traveller connected to the wrong pair, inverting the logic for some combinations Fix: Isolate the circuit. At the 4-way switch, use a continuity tester to map which terminal connects to which when the switch is in each position. Verify that IN1–OUT1 and IN2–OUT2 pair in straight position, and IN1–OUT2, IN2–OUT1 pair in crossed position. Correct any misassigned terminal.
Light is permanently on or permanently off regardless of switch positions: Cause: Traveller conductors short-circuited together, or one traveller connected to neutral or earth instead of the correct terminals Fix: Isolate the circuit. Measure resistance between the two traveller conductors at each switch position from a disconnected point. They should be open-circuit when measured at the cable end (with no switches in circuit). A near-zero reading indicates a short. Also verify that neutral and earth are not inadvertently connected to traveller terminals.
Fixture flickers or buzzes intermittently: Cause: Loose terminal connection on a traveller conductor, worn switch contacts, or (with LED lamps) trailing-edge dimmer incompatibility Fix: Tighten all terminal screws — switch terminals are a frequent source of arcing connections. Check switch contacts for signs of burning or pitting. If the fixture uses LED lamps, ensure the driver and switches are compatible (some LED drivers are sensitive to the resistance of traveller cables and switch contacts).

Frequently asked questions

What is the difference between a 3-way and a 4-way switch?

A 3-way switch (North American terminology) or two-way switch (UK/IEC) has three terminals: common, and two travellers. It routes its common terminal to one of the two travellers depending on switch position. A 4-way (North American) or intermediate (UK/IEC) switch has four terminals arranged as two input travellers and two output travellers, and swaps their connections when toggled. Only 4-way/intermediate switches can be added in the centre of a multi-location circuit.

How many 4-way switches can I add to one circuit?

Theoretically unlimited — each additional 4-way switch adds one control location. Practical limitations include the permitted cable run lengths for the traveller conductors and the number of conductors in the conduit or cable route, not any inherent limit in the switching logic. Each additional location requires one additional 4-way switch and one additional two-conductor traveller cable between switch positions.

Why does my 4-way switch wiring not work in all combinations?

If the light changes state from some switch positions but not others, one of the traveller conductors is likely crossed incorrectly at the 4-way switch terminals. The IN pair and OUT pair must each connect to the correct set of terminals; swapping a wire within a pair (rather than between pairs) breaks the logic. Use a multimeter in continuity mode to trace each traveller conductor and verify correct terminal assignment.

Do I need all three switches to be 4-way switches?

No. Only the switches in the middle positions of the circuit are 4-way (intermediate) switches. The two end switches must be 3-way (two-way) switches — one at each end of the traveller chain. If you have three switch locations, you need two 3-way end switches and one 4-way middle switch. Four locations require two 3-way end switches and two 4-way middle switches.

Can I install a 4-way switch circuit myself?

Mains voltage switch wiring is regulated in most countries. In the UK, this type of work is notifiable under Part P of the Building Regulations and must be carried out or verified by a registered electrician. In North America, a permit and inspection by the authority having jurisdiction (AHJ) is typically required. In Australia and New Zealand, all mains wiring must be performed by a licensed electrician. Do not perform this work yourself unless you hold the required qualifications and permits.

How do I wire a 3-way switch diagram to control one light?

To control one light from two locations using 3-way switches, run the hot supply to the common terminal of the first 3-way switch, connect the two traveller wires between the traveller terminals of both switches, and run the switched wire from the common terminal of the second switch to the light fixture. The neutral connects directly from the supply to the fixture without passing through either switch. This is the standard 3-way circuit with no 4-way switches needed; add a 4-way switch in the traveller loop only when a third (or additional) control location is required.