Wiring a 4-Way Switch Diagram

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

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

A 4-way switch (called an intermediate switch in UK/Commonwealth wiring) is inserted between two 3-way (or 2-way) switches to extend light control to three or more locations — each additional 4-way switch adds one more control point without changing the end switches.

When you need to control a single light from three or more locations — a long hallway with a switch at each end and one in the middle, or a large room with multiple entry points — the solution is a 4-way switch inserted into the traveller conductors of a standard 3-way (2-way in UK terminology) circuit.

The concept builds directly on the 3-way (2-way) circuit: two traveller conductors run between the two end switches. The 4-way switch sits in the middle of these two travellers and has four terminals. Internally, it can connect in two configurations: 'straight through' (T1-T1 and T2-T2) or 'crossed over' (T1-T2 and T2-T1). Each time you operate the 4-way switch, it alternates between these two states, effectively toggling what the downstream end switch 'sees' on its travellers — and therefore changing the state of the light.

US/UK Terminology: A '4-way switch' in the USA corresponds to an 'intermediate switch' in the UK. The two end switches remain 3-way switches (US) or 2-way switches (UK). The 4-way/intermediate is never placed at the ends of the circuit.

Scaling: If you need four control locations, add a second 4-way/intermediate switch in series with the first, still between the same pair of end switches. You can add as many 4-way switches as needed — each one intercepts the same pair of traveller conductors.

The power routing options are the same as for a 3-way circuit: power can enter at one of the end switches or at the light. The critical point is that the two traveller conductors must run continuously through every 4-way switch in the chain without interruption of the neutral or earth.

In the UK using BS 7671 conventions, the intermediate switch typically arrives on a 3-core + earth cable from one direction and leaves on a 3-core + earth cable in the other direction, with conductors re-identified as switched live conductors where required.

How to wire wiring a 4 way switch

Plan the cable runs before starting any work Identify where each switch will be located. The two end switches are standard 3-way/2-way switches; any middle positions require 4-way/intermediate switches. Plan cable runs: you need 3-core + earth cable between every switch in the chain, with the two travellers running through every 4-way switch box.
Isolate the circuit at the consumer unit and verify dead Switch off and lock out the MCB or fuse at the consumer unit. Test for voltage at all switch and light fitting locations with a calibrated voltage tester. Do not assume the circuit is dead based only on the MCB position.
Wire the first end switch (3-way/2-way) Connect the supply live to the COM terminal of the first end switch. Connect the two traveller cores from the cable running toward the next switch (either a 4-way or the second end switch) to the L1 and L2 terminals. Pass neutral and earth through without interruption.
Wire the 4-way switch(es) Connect the traveller pair arriving from the previous switch to one pair of terminals on the 4-way switch (e.g. the left pair). Connect the traveller pair leaving toward the next switch to the other pair (e.g. the right pair). The exact terminal arrangement depends on the switch manufacturer — follow their wiring diagram precisely, as terminal labelling varies.
Wire the second end switch (3-way/2-way) Connect the two arriving traveller conductors to the L1 and L2 terminals of the second end switch. Connect the switched live going to the light fitting to the COM terminal of this switch.
Re-identify conductors as required Any conductor that is not its declared colour function (e.g. a blue/black core used as a switched live) must be re-identified with correct colour sleeving at every termination. Follow BS 7671, SANS 10142, or your local equivalent.
Test all switch combinations before closing covers Restore power and test every switch position — with three locations there are eight possible switch combinations. Operating any single switch must always change the state of the light. If any combination fails to toggle correctly, switch off, identify which switch has the fault (by process of elimination), and check its traveller terminations.

Specifications

US terminology	4-way switch (four terminals, no common) inserted between two 3-way switches
UK/Commonwealth terminology	Intermediate switch (four terminals, no common) inserted between two 2-way switches
Number of control locations	3 locations = two 3-way + one 4-way; 4 locations = two 3-way + two 4-way; etc.
Cable between each switch	3-core + earth (two travellers plus additional conductor)
Switch rating (residential)	6 A or 10 A at 230/250 V AC (UK/SA/AU); 15 A at 120 V AC (USA residential)
Supply voltage (UK/SA/AU)	230 V AC, 50 Hz
Supply voltage (USA)	120 V AC, 60 Hz (residential)
Applicable standards	BS 7671 (UK), SANS 10142-1 (SA), AS/NZS 3000 (AU/NZ), NEC NFPA 70 (USA)

Safety warnings

Isolate the circuit at the consumer unit before touching any wiring. In a multi-way switching circuit, traveller conductors are live during normal operation even when the light is off — verify dead with a voltage tester at every switch position before proceeding.
Fixed electrical installation work must be carried out by a competent person in compliance with the applicable wiring regulations for your region: BS 7671 (UK), SANS 10142-1 (South Africa), AS/NZS 3000 (Australia/NZ), or NEC/NFPA 70 (USA). Certificates or notification may be required.
Never connect a 4-way/intermediate switch at an end position where a 3-way/2-way switch is required — the circuit will not operate correctly and the error may be difficult to diagnose without understanding the full circuit.
Earth continuity must be maintained at every switch box and at the light fitting. Do not interrupt the earth conductor at any point in a multi-way circuit.
Ensure all core re-identifications (colour marking) are completed at every termination point before closing switch covers. An unmarked switched live conductor creates a hazard for future workers.

Tools needed

Non-contact or multimeter voltage tester
Digital multimeter with continuity function
Insulated screwdrivers (flathead and Phillips)
Wire strippers
Side cutters
Conductor re-identification sleeving or tape (per local wiring regulations)
Cable clips and installation tools for surface or concealed wiring
Torch/headlamp for working in switch boxes

Common mistakes

Installing a 4-way switch at the end of the circuit instead of the middle — the ends must always be 3-way (2-way) switches with a COM terminal.
Connecting both pairs of travellers to the same pair of terminals on the 4-way switch, rather than one pair to each side — the light may work in some combinations but not all eight.
Using 2-core cable between switch positions — you need 3-core + earth between every switch in a multi-way chain to carry both travellers.
Not testing all eight switch position combinations (for a 3-location circuit) — a wiring error may allow most combinations to work but fail in one or two specific positions.
Confusing 4-way switch terminal labels between manufacturers — terminal labelling is not standardised; always use the diagram printed on the switch body or in the manufacturer's instructions.
Omitting earth connections at metal switch plates in any position in the chain — all metalwork must be bonded.

Troubleshooting

Light works in some switch combinations but not all: Cause: Traveller connections at the 4-way switch are wrong — both pairs on the same side, or connections crossed within one pair Fix: Switch off at consumer unit and verify dead. Remove the 4-way switch cover and check that the two traveller conductors from one cable connect to one pair of terminals, and the two travellers from the other cable connect to the opposite pair. Consult the switch manufacturer's diagram — do not assume terminal layout.
No switch position produces light: Cause: Open circuit — broken conductor, open circuit at a terminal, blown fuse, or tripped MCB Fix: Check the consumer unit for a tripped breaker. Then use a multimeter to trace continuity through each section of the circuit: supply to COM of first switch, travellers through to second end switch, switched live to light fitting, neutral back. Isolate each faulty section in sequence.
Light stays on permanently regardless of any switch: Cause: Two travellers shorted at a switch position, or a 4-way switch internal fault Fix: Isolate circuit. Disconnect the traveller pairs at each 4-way switch individually and test for short circuit between them using a multimeter. Replace any switch with a short across its internal contacts.
Newly added 4-way switch position does not control the light: Cause: The 4-way switch has been inserted in only one traveller conductor rather than interrupting both — effectively making it a single-pole switch in one traveller with no effect on the other Fix: Confirm that BOTH traveller conductors pass through the 4-way switch. If only one traveller is connected to the switch and the other bypasses it, reconnect so both travellers terminate at the 4-way switch terminals.

Frequently asked questions

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

There is no practical electrical limit — you can add as many 4-way (intermediate) switches as the circuit design requires. Each additional 4-way switch adds one more control point. The two traveller conductors simply pass through every intermediate switch in the chain, from one 3-way/2-way end switch to the other.

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

They are the same device with different names. '4-way switch' is the US/Canadian term, referring to its four terminals. 'Intermediate switch' is the UK/Commonwealth term, referring to its position in the circuit between two 2-way end switches. The terminal configuration and function are identical.

Can I replace a 3-way switch with a 4-way switch by mistake?

Yes, and it will result in the light only working in some switch combinations. A 4-way switch has four terminals and no designated 'common' — it should never be used at the ends of the circuit. If a light only works in some switch combinations after wiring, check that the end positions have 3-way (2-way) switches and the middle positions have 4-way (intermediate) switches.

Does a 4-way switch have a common terminal?

No. A 4-way switch has four terminals used only for the two traveller pairs — there is no common terminal. Compare this to a 3-way switch, which has one common terminal and two traveller terminals. Mistaking a 4-way for a 3-way (or vice versa) at the end positions is one of the most common wiring errors in multi-way circuits.

Why does my light only work in some combinations of three switches?

If only some switch position combinations produce light, the 4-way switch traveller connections are likely crossed — both pairs of travellers may be entering on the same side of the switch instead of one pair each side. Check the manufacturer's wiring diagram for your specific 4-way switch, as terminal labelling varies. Swapping one pair of traveller connections at the 4-way switch will usually resolve it.