4-Way Switch Wiring
Two diagrams and the tests that sort traveler pairs in a box.
Compiled by DIY Repair Guide · reviewed 2026-09-14 ·how we research these
A 4-way switch lets you control one or more lighting fixtures from three or more separate wall locations. In any 4-way switching setup, the 4-way switch always sits between two 3-way switches along the traveler line. It has four traveler terminals in two pairs and no common. To wire the switch correctly, connect the incoming traveler pair from the first 3-way switch to the input terminals, and connect the outgoing traveler pair heading toward the second 3-way switch to the output terminals.
Before touching any terminals or stripping insulation, turn off power at the circuit breaker or fuse box and verify that the circuit is dead with a reliable voltage tester. A 4-way switch never connects directly to the incoming hot line or to the light fixture itself. If you connect traveler wires from different cables to the same pair of terminals, the circuit fails to operate normally.
How a 4-way Switch Works
A standard 3-way switch is a single-pole double-throw (SPDT) switch that directs current from a single common (COM) terminal to one of two traveler conductors. You can read our detailed guide to 3-way switch wiring to see how those two outer endpoints direct current. A 4-way switch sits between those travelers and swaps them.
According to physics tutorial documentation published by Wake Forest University, a 4-way switch has two mechanical positions. In the first position, the internal contacts connect straight through from left to right, allowing the traveler conductors to pass without altering their path. In the second position, the internal mechanism cross-connects the contacts in an X pattern. This cross connection swaps which conductor feeds forward to the next switch.
Because flipping the handle either maintains or crosses the two paths, operating the 4-way switch toggles the fixture on or off regardless of the positions of the two flanking 3-way switches.
4-way Switch Wiring Diagram
In a standard multi-location lighting circuit, the power source feeds into one end of the switch string and the fixture connects to the opposite end. Educational material from Purdue Extension notes that when wiring or troubleshooting these combinations, one 3-way common terminal connects to the continuous power feed and the other 3-way common terminal connects to the light fixture.
The diagram below illustrates the typical flow when power arrives at the first switch box. The incoming hot connects to the common screw of the first 3-way switch. Two traveler conductors leave that switch and land on the input pair of the 4-way switch. A second set of traveler conductors leaves the 4-way switch output pair and runs to the traveler terminals of the second 3-way switch. Finally, the common terminal on that second 3-way connects directly to the light. The neutral conductor bypasses all three switch mechanisms completely and ties straight into the light fixture.
As Purdue Extension diagrams demonstrate, alternative layouts also exist, including configurations where constant power enters the light fixture box first before dropping down to the switch boxes. Wake Forest University's tutorial and Lutron's installation instructions both allow more than one 4-way, so you can insert additional 4-way switches into the traveler lines if you need to control the fixture from four, five, or more wall stations.
Which Wires Go Where on a 4-way Switch
A 4-way switch features four main circuit terminals plus a green grounding screw. Because terminal layouts vary across brands, you must recognize terminal groupings rather than relying strictly on physical screw locations. Manufacturer specifications from Lutron state that terminals on a 4-way switch are arranged in pairs of same-colored screws or explicitly stamped with IN and OUT designations.
In instructions for the Leviton A5621 and A5624 switches, Leviton labels traveler connections between 3-way switches as brass screw to brass screw, and shows the 4-way connections running brass screw to black screw. On that specific Leviton model, one traveler pair connects to the two brass screws while the opposite traveler pair connects to the two black screws. This is one manufacturer example. Screw coloring and stamping vary across brands, so the instruction sheet for your exact device remains the final authority. On any 4-way switch, a dark screw is never a common terminal. It is simply half of a traveler pair.
| Terminal | What lands there | How to spot it |
|---|---|---|
| Input pair | Both traveler conductors from the first 3-way switch box | Pair of same-colored screws or stamped IN |
| Output pair | Both traveler conductors heading to the next switch box | Pair of same-colored screws of contrasting color, or stamped OUT |
| Ground terminal | Bare copper or green insulated equipment grounding conductor | Green ground screw |
Identifying Wires in an Existing Box
If you are replacing an existing switch, shut off the breaker, test that the box is dead, take a clear photo of the original connections, and label which pair of conductors lands on each terminal set before unhooking anything. Labeling each cable pair preserves the circuit layout without guessing. If the wires are already loose in the box, you must test the conductors to identify which two belong to the incoming traveler line and which two head outward.
A 4-way switch has no common wire. Common terminals exist only on the two 3-way switches flanking the circuit. The four wires in your 4-way box consist entirely of two traveler pairs. According to Purdue Extension, standard cable assemblies include two-conductor (black and white) and three-conductor (black, red, white) types. In switch runs, a white conductor can serve as a hot traveler, but it must be marked as a hot conductor, for example with black marker.
To identify terminals on an unlabeled 4-way switch out of the wall with power disconnected, Wake Forest University's 4-way troubleshooting page describes an ohmmeter procedure. Attach one test lead from your meter to any single screw terminal. Measure the electrical resistance to each of the other three screws while toggling the switch handle between its two positions. The one terminal that shows infinite resistance in both toggle positions forms an isolated pair with your first terminal. Those two screws are the IN pair, and the other two are the OUT pair. You can review our guide on how to check continuity with a multimeter to verify these resistance readings.
To sort out unidentified traveler conductors inside the box, use a two-person continuity test with the circuit breaker turned off. Have person A stand at the first 3-way switch box and touch two conductors together. At the 4-way box, person B tests resistance across wire combinations with a meter. When person A repeatedly connects and disconnects that pair, the meter reading at the 4-way box alternates between near-zero resistance and infinite resistance. That alternation proves those two conductors form the traveler pair arriving from that first switch box. Connect that confirmed pair to the 4-way switch IN terminals, and connect the remaining traveler pair to the OUT terminals.
How to Wire a 4-way Switch, Step by Step
Conductor size must match your circuit breaker rating. Consult our wire gauge chart to confirm adequate wire gauge for the ampacity of your branch circuit. Follow these step-by-step instructions to wire the switch:
- 1. Turn off power at the breaker panel. Switch off the circuit breaker or remove the fuse that controls the lighting branch circuit.
- 2. Confirm the circuit is dead. Test all conductors inside the switch box using a reliable tester to ensure no live voltage remains. Check our guide comparing a multimeter vs voltmeter for proper verification procedures.
- 3. Document and tag existing conductors. Photograph the original switch before removing screws. Mark the two wires connected to the first pair of terminals with tape to keep the incoming and outgoing pairs distinct.
- 4. Pair the conductors correctly. Confirm that the two traveler wires arriving from the first 3-way switch land together on the 4-way switch input pair. Confirm that the two travelers heading to the second 3-way switch land together on the output pair.
- 5. Terminate the conductors securely. For example, Leviton's instruction sheet specifies copper or copper-clad wire only. It permits side-wiring up to #12 American Wire Gauge (AWG) by stripping roughly 3/4 inch and looping clockwise 3/4 turn around the screw, or back-wiring up to #10 AWG by stripping about 1/2 inch into the clamp. Check your manufacturer documentation for required strip lengths and recommended torque values.
- 6. Bond the equipment grounding conductor. Fasten the bare copper or green insulated wire to the green grounding screw on the switch yoke to bond the device securely.
- 7. Mount the switch and test all positions. Carefully fold the conductors into the back of the electrical box, secure the switch with mounting screws, attach the wallplate, and restore breaker power. Toggle each of the three switches independently to verify the light changes state from every location.
Smart Switches and the Neutral Wire
Many smart switches need constant power for their radios and electronics. According to product support documentation from Leviton, standard Wi-Fi in-wall smart devices require an active neutral conductor inside the junction box to complete their internal power circuit.
A mechanical 4-way switch never uses a neutral. In older homes, switch boxes frequently contain only the traveler and hot conductors without a neutral line present. Leviton notes that no-neutral smart lines exist specifically for retrofitting homes built before widespread adoption of the 2011 National Electrical Code (NEC) requirement for neutrals in switch boxes. If you plan to install a smart 4-way system, check whether the product needs a neutral, and do not assume a white wire in the switch box is one.
Troubleshooting 4-way Switch Circuits
When a newly installed 4-way circuit fails to operate properly, a common cause is an accidental split between the traveler pairs. If one conductor from the first 3-way switch and one conductor from the second 3-way switch are landed together on the same input terminal pair, the circuit cross-connects incorrectly. In one position of the 4-way switch, both travelers heading to the second 3-way join together, which leaves the light fixture completely dead. In the other position, the circuit might function normally. This error creates a confusing lockout where the light operates only when the 4-way switch sits in one specific toggle position. Resolving this problem requires shutting off power, testing the wires to re-identify the cable pairs, and placing one complete pair on IN and the other on OUT.
A second common failure occurs on one of the 3-way switches rather than the 4-way device. If the incoming hot or the wire to the light lands on a traveler screw instead of the common on a 3-way switch, the light responds only in some switch combinations. Check our 3-way switch wiring guide to isolate and correct misplaced common conductors at the outer boxes.
A third issue arises when someone installs the wrong physical device into a junction box. Installing a 3-way switch into a 4-way location leaves one traveler disconnected, while installing a 4-way switch at the end of the line leaves an extra terminal unconnected. Verify hardware by counting screw terminals: a 3-way switch has three insulated circuit screws plus a ground, while a 4-way switch features four insulated circuit screws plus a ground.
Differences Between 3-way and 4-way Switches
While both devices control fixtures across multiple locations, their electrical roles, terminal counts, and switching actions differ completely.
| Feature | 3-way Switch | 4-way Switch |
|---|---|---|
| Circuit terminals | Three circuit screws (one dark common, two travelers) plus ground | Four circuit screws arranged in two traveler pairs, plus ground |
| Internal mechanism | Single-pole double-throw (SPDT) routing common to one traveler | Two-position reverser passing travelers straight through or crossed |
| Position in circuit | Located strictly at the two physical ends of the switch run | Located anywhere along the traveler run between the two 3-way switches |
| Quantity per circuit | Always exactly two switches per multi-switch circuit | Any quantity from zero upward, depending on total control points |
| Direct line or load ties | One common connects to power source. Other common connects to light | Never connects directly to incoming continuous power or the light fixture |
When to Call a Licensed Electrician
While replacing a switch is a manageable task when existing cables are clearly marked, complex junction boxes warrant professional intervention. If you open a switch box and find mixed traveler pairs, unidentifiable conductor splices, or deteriorated insulation that prevents reliable continuity testing, stop work immediately.
Manufacturer guidelines from Leviton state clearly that if you are uncertain about any part of the wiring instructions, you should consult a licensed electrician. Also hire a licensed electrician to run new three-conductor cable for another switch location or a neutral for a smart switch. Electrical work must comply with local building codes and the National Electrical Code to maintain safe home operation.
Never perform work on energized circuits. Always switch off the branch circuit breaker and verify the absence of voltage across all conductors with an approved tester before handling any switch terminals.
Common questions
Which wires go where on a 4-way switch?
The two traveler conductors arriving from the first 3-way switch connect to the 4-way switch input pair terminals. The two traveler conductors heading to the second 3-way switch connect to the output pair terminals. The equipment grounding wire connects to the green ground screw.
Is there a difference between a 3-way and 4-way switch?
Yes. A 3-way switch has three circuit screws including one common terminal and routes power between two traveler lines. A 4-way switch has four circuit screws arranged in two traveler pairs, possesses no common terminal, and either passes travelers straight through or crosses them.
Can I wire a 4-way switch as a single pole?
A 4-way switch internal contact mechanism can technically make and break a single path, but it is not intended for that application. You should install a standard single-pole switch for single-location control, and consult an electrician if you are unsure about device selection.
How do you wire a 4-way switch with two 3-way switches?
Connect continuous hot power to the common terminal of the first 3-way switch. Run its two travelers to the input pair of the 4-way switch, run travelers from the 4-way output pair to the second 3-way switch, and run that second common terminal to the light fixture.